JPH05115794A - Waste gas purifying apparatus - Google Patents

Abstract

PURPOSE:To improve heating properties and achieve high purification efficiency by making the width of a honeycomb-like structural body in waste gas flow direction become smaller toward the external circumference from the center part and making a purification catalyst to be carried on the honeycomb body. CONSTITUTION:Regarding a waste gas purifying apparatus A composed of an electrothermal heat generating-type catalyst H and a main catalyst M set behind the catalyst H, the electrothermal heat generating-type catalyst H is composed of honeycomb bodies H1 having the width 1 in waste gas flow direction which becomes smaller toward the external circumference from the center part of the honeycomb-like structure and carries a waste gas purification catalyst. Consequently, since a waste gas can be heated uniformly to sufficiently and properly high temperature for catalytic reaction in the electrothermal heat generating-type catalyst H, the waste gas purifying function, which conventionally becomes a problem especially at the time of the cold start, is remarkably improved. Also, since the electrothermal heat generating-type catalyst H itself carries a purification catalyst, the whole purifying function of the purifying apparatus A is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to an exhaust gas purifying apparatus which is used as an exhaust gas purifying means for an automobile by being inserted in the middle of an exhaust pipe. More specifically, the present invention incorporates a heating means capable of significantly improving a major drawback of this type of exhaust gas purification apparatus, that is, a problem of low exhaust gas purification rate at engine start (cold start). It relates to an exhaust gas purification device.

[0002]

2. Description of the Related Art Conventionally, as a catalyst supporting base which is a main constituent element of this type of exhaust gas purifying apparatus, a ceramic monolith type using a ceramic material such as cordierite and a metal (metal) type are used. A monolith type is known. Particularly in recent years, a metal monolith type has been actively researched and developed from the viewpoints of mechanical strength, durability, ventilation resistance, purification efficiency, downsizing of a device, and the like. In the following description, the latter metal monolith type will be mainly described for convenience of description. A metal monolith-type exhaust gas purifying apparatus generally stacks flat plate-shaped strips made of heat-resistant thin steel plates and corrugated strips formed by corrugating the thin steel plates so as to have mutual contact portions. However, a large number of mesh vent holes (hereinafter, also referred to as cells) for the exhaust gas passage are formed in the axial direction, which are manufactured by stacking them in a spiral shape or by stacking them in layers. It is composed of a honeycomb laminated body (hereinafter, referred to as a honeycomb body) and a cylindrical metal case having both ends opened for filling and fixing the honeycomb body. The honeycomb body and the metal case are formed so as to withstand the thermal expansion and thermal stress that occur in the high temperature of the exhaust gas itself and the high temperature atmosphere due to the exothermic reaction between the exhaust gas and the purification catalyst. It is firmly fixed by brazing or welding so that it can withstand severe vibrations during traveling. Needless to say, the abutting portions of the flat band member and the corrugated plate member forming the honeycomb body are fixed by various methods.

The major problems in this type of exhaust gas purifying apparatus are as follows. That is, at the time of engine start (at the time of cold start), the optimum temperature at which the exhaust gas purifying catalyst such as Pt, Pd, and Rh carried on the wall surface of the metal honeycomb body efficiently causes a catalytic reaction with the exhaust gas. This means that the conditions have not been reached, and most harmful substances such as CO (carbon monoxide) and HC (hydrocarbon compounds) emitted from the engine are not purified but are released into the atmosphere. ..

Various proposals have been made in order to solve the problems at the time of starting the engine (at the time of cold starting). For example, in (i) Japanese Utility Model Publication No. 63-67609, a converter using a ceramic monolith type as a main catalyst supporting base is manufactured in advance in a honeycomb shape at a portion near the exhaust gas upstream side of the main catalyst supporting base. A method of coating the metal carrier with alumina, and disposing a metal monolith catalyst capable of conducting electricity, (ii)
No. 4316 has a method of arranging a far infrared heater on the outer peripheral portion of the catalyst body, and (iii) No. 3-10022 of actual Kaihei has a heater on the front surface (upstream side of exhaust gas) of a monolith type catalyst. A method of arranging a rectifying plate for rectifying exhaust gas on the front surface of the heater has been proposed. However, in these conventional proposals, in view of the requirement that the temperature of the honeycomb body that performs the heater function should be raised sufficiently high to efficiently carry out the catalytic reaction,
It is not completely satisfactory because the temperature rise temperature is insufficient or the cost is increased to solve the problem.

[0005]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The present invention has been made to solve the problems found in the above-mentioned conventional honeycomb body. The present inventors have made various studies on a technique for raising the temperature of the honeycomb body, particularly the entire inside of the honeycomb body, to a uniform and sufficiently high temperature during cold start. In particular, the actual development 63 described in the prior art
The inventors have earnestly studied the improvement of the electric heating type honeycomb body for an exhaust gas purifying apparatus proposed in Japanese Patent No. 67609 or the like.

As a result, the inventors of the present invention have applied the flat plate-shaped strip material and the corrugated plate-shaped strip material made of a heat-resistant thin metal plate proposed in Japanese Utility Model Laid-Open No. 63-67609 described above. A pre-heater is manufactured by stacking so as to be in contact with each other to form a wound-type honeycomb body, and disposing an electrode material at the central portion and the outer peripheral portion of the honeycomb body. It is coated with alumina, but it is recognized that this is because the catalyst for purifying exhaust gas is supported on the formed coating layer.), However, the following defects have been found. For example, in the honeycomb body as an electric heating type preheater having the above-mentioned structure, an outer peripheral electrode material of the honeycomb body is connected to a positive electrode and a central electrode material is connected to a negative electrode with respect to an external power source part (battery etc.). When energized, (a) the surface area of the honeycomb body with respect to the surface area of the outer peripheral electrode material (because the honeycomb body is fixed in the conductive cylindrical metal case, the entire metal case serves as the outer peripheral electrode material). The ratio of the current-carrying area formed by the flat strip and the corrugated strip per unit volume in the outer peripheral portion and the vicinity thereof,
(B) In the ratio of the current-carrying area formed by the flat plate-shaped strip material and the corrugated plate-shaped strip material per unit volume in the central portion and the vicinity portion of the honeycomb body to the surface area of the central electrode material (for example, Ni round bar material), Since the former (a) is overwhelmingly larger, the current density flowing through the walls of each cell of the former is much smaller than that of the latter, in other words, in the outer peripheral portion of the honeycomb body and its vicinity due to energization. The heat generation amount obtained by resistance heating is smaller than the heat generation amount obtained by resistance heating in the central portion of the honeycomb body and the vicinity thereof. As a result, the temperature inside the honeycomb body as the preheater becomes uneven.

As is well known, this type of electric heating type honeycomb body (H ') having a preheater function is used by being incorporated in the exhaust gas purifying apparatus (A) in the mode shown in FIG. .. FIG. 8 is a cross-sectional view in which a part of an exhaust gas purifying device (A) incorporating a conventional electric heating type honeycomb body (H ′) is omitted. As shown in the figure, with respect to the exhaust gas flow (F), an electric heating type honeycomb body (H ') is carried on the upstream side of the exhaust gas, and an exhaust gas purifying catalyst such as Pt, Pd, Rh is carried on the downstream side. An exhaust gas purifying device (A) is configured by disposing a main catalyst (M) in a metal case (C). Then, the central electrode material (B ₁ ) and the outer peripheral electrode material (B ₂ ) of the electric heating type honeycomb body (H ′) are connected to the external power source part (4) by conducting wires (5, 6). To be done. It should be noted that in the disposition of the honeycomb body (H ′), it is necessary to pay attention to the insulating property from other members, but this is omitted in FIG. 8 for simplification.

As described above, in the conventional type exhaust gas purifying apparatus (A) shown in FIG. 8, the electric heating type honeycomb body (H ') having a pre-heater function does not uniformly heat and heat inside due to the electric current. Exhaust gas passing through the inside is unevenly heated and reaches the main catalyst (M) on the downstream side. That is, the exhaust gas is not uniformly heated to the optimum temperature for the catalytic reaction and flows into the main catalyst (M), and as a result, the optimum exhaust gas purification cannot be achieved. In addition, in the conventional energized heating type honeycomb body (H ′),
Due to the above-mentioned difference in current density, when the central part is heated to an appropriate temperature, the peripheral part becomes low temperature, but when the peripheral part is heated to an appropriate temperature to eliminate this, the central part, especially the part near the central electrode material overheats, and in extreme cases In this case, the honeycomb body (H ') is melted down (damaged), and the vibration resistance durability (mechanical strength) of the honeycomb body (H') is greatly impaired.

On the other hand, the present inventors have found that in the conventional structure of the honeycomb body (H ') having a preheater function,
As described in (a) and (b) above, when the means for making the current-carrying areas for the electrode materials (the central electrode material B ₁ and the outer peripheral electrode material B ₂ ) approximately the same is taken, the inside of the honeycomb body is made uniform. It has been found that it is heated and that thereby a high exhaust gas purification efficiency is achieved. Further, in this case, in order to provide the exhaust gas purifying ability also on the side of the honeycomb body, in particular, H
When an oxidation-reduction catalyst that oxidizes C (hydrocarbon compound) and CO (carbon monoxide) and a redox catalyst that can also reduce NOx (nitrogen oxide) are supported on the wall surface of the honeycomb body, the catalytic reaction It was found that the heating characteristics were improved due to the exothermic reaction, which was effective for exhaust gas purification at engine start (cold start). Under such an aspect, it was also found that the honeycomb body can be used as a substitute for the conventional main catalyst (M) in addition to the use as a precatalyzer. The present invention is based on the above-mentioned findings, and an energization heat generation type exhaust gas purification device, in particular, an energization heat generation type which is a main component thereof, and a honeycomb body having a catalyst supported thereon and having an exhaust gas purification ability (hereinafter, simply referred to as energization It is intended to provide an exothermic catalyst.

[0010]

The present invention will be summarized as follows.
The present invention relates to an exhaust gas purifying apparatus comprising an energized exothermic catalyst (H) or a main catalyst arranged at the rear of the energized exothermic catalyst (H), wherein the energized exothermic catalyst (H) is (i) A honeycomb-shaped structure produced by stacking flat plate-shaped strips and corrugated strips made of thin metal plates so as to abut each other, and as the honeycomb-shaped structure goes from the center to the outer periphery. The honeycomb body (H ₁ ) has a width (l) in which the width in the exhaust gas flow direction gradually decreases, and (ii) the honeycomb body (H ₁ ) carries an exhaust gas purification catalyst. And (iii) the honeycomb body (H ₁ )
The present invention relates to an exhaust gas purifying device characterized in that an electrode material for connecting to an external power source is arranged in the central portion and the outer peripheral portion.

The technical construction and embodiments of the present invention will be described below with reference to the drawings. Needless to say, the present invention is not limited to the illustrated one.

FIG. 1 is a sectional view in which a part of an electric heating type catalyst (H) of the first embodiment of the present invention is omitted, and FIG. 2 is a perspective view. The energizing heat generating catalyst (H) of the present invention is used as a precatalyzer in place of the conventional energizing heat generating honeycomb body (H ') shown in FIG. That is, it is arranged and used as a preheater on the upstream side of the main catalyst (M) with respect to the exhaust gas flow direction (F). In addition, the energized exothermic catalyst (H) of the present invention may be used as a main catalyst instead of the main catalyst (M) in some cases. The energized heat generation type catalyst (H) of the present invention is a conventional energized heat generation type honeycomb body (H
Compared with ´), it differs greatly in the following points.

(A) Conventional electric heating type honeycomb body (H
′) Is a flat strip (1) made of a heat-resistant thin metal plate and having a predetermined width (l ′) as described above and as shown in FIG.
And a corrugated strip (2) are stacked so that they come into contact with each other, and they are wound together in a spiral shape to produce a wound type honeycomb body, and an electrode material is provided at the center and the outer periphery. (B ₁ , B
₂ ) is provided. As shown in FIG. 2, a large number of exhaust gas net-like ventilation passages (cells) (3) are automatically formed by winding and laminating the flat strip and the corrugated strip. Therefore, as shown in FIG. 8, the thickness of the width of the honeycomb body (H ′), that is, the thickness (1 ′) in the exhaust gas flow direction (F) is constant. (B) On the other hand, the honeycomb body (H ₁ ) forming the electric heating catalyst (H) of the present invention is the same as the conventional one in the sense of a honeycomb structure, but FIGS. As shown in FIG. 2, the width (l) in the exhaust gas flow direction (F) increases from the central portion of the honeycomb body (H ₁ ) to the outer peripheral portion thereof.
It gradually increases (decreases) from large to small. In addition,
Electrode materials are respectively arranged in the central portion and the outer peripheral portion of the honeycomb body (H ₁ ), and the widths of the electrode material (B ₁ ) in the central portion and the electrode material (B ₂ ) in the outer peripheral portion are also as described above. The difference (B ₁ > B ₂ ) in the width (l) between the central portion and the outer peripheral portion of the honeycomb body (H ₁ ) may be dealt with.

The above-mentioned differences have important significance. That is, for example, when electricity is applied under the mode of FIG. 1, more specifically, the outer peripheral electrode material (of the honeycomb body (H ₁ ) (with the lead wires (5, 6) to the external power source section (4) ( B ₂ ) is connected to the positive electrode side and the central electrode material (B ₁ ) is connected to the negative electrode side, and when electricity is applied, the outer peripheral electrode material (B ₂ ) → the central electrode material (B ₁ ) In the current-carrying path through which electricity flows through the wall (which naturally consists of the flat plate-shaped strip (1) and the corrugated plate-shaped strip (2)), the honeycomb body (H
_In the width of the electrode material itself, B ₁ > B ₂ reflecting the fact that the width ( ₁ ) of ₁ ) is gradually increased from the outer peripheral portion to the central portion.
Since the above relationship is established, electricity having substantially the same density flows in any part inside the honeycomb body (H ₁ ).
In other words, electricity will flow through the conductors (each cell wall) having substantially the same resistance value in the energization path, whereby uniform resistance heating can be obtained. This is an advantage that the width of the central portion of the honeycomb body (H ₁ )> the width of the outer peripheral portion, that is, B ₁ > B ₂ correspondingly. The above points are related to the outer peripheral electrode material (B
_Since the ratio of the surface area of ₂ ) and the current-carrying area of the vicinity thereof and the ratio of the surface area of the central electrode material (B ₁ ) and the current-carrying area of the vicinity thereof are substantially the same in the present invention, it is easy to It is understandable.

Further, another major characteristic feature of the electric heating type catalyst (H) of the present invention is that when the electric heating type catalyst (H) is used in combination with a main catalyst (M) described later, The exhaust gas purifying catalyst is carried not only on the latter side but also on the energized exothermic catalyst (H) itself. As described above, the energizing heat generation type catalyst (H) of the present invention can be used as the main catalyst (M). As is well known, HC (hydrocarbon compounds) and CO (carbon monoxide) in exhaust gas are oxidized catalysts (Pt, Pd, Cr, V, Cu, etc.).
Under heat, it is rendered harmless to CO ₂ and H ₂ O by an exothermic reaction. Also, H emitted in the exhaust gas near the stoichiometric air-fuel ratio
Redox that purifies C, CO and NOx simultaneously (three-way)
Catalysts (Pt-Rh system, Pt-Pd-Rh system, etc.) are well known, and these exhaust gas components are CO ₂
Or oxidized to H ₂ O or reduced to N ₂ . Even in a three-way catalyst system, the catalytic reaction progresses exothermically as a whole. In the present invention, the meaning of carrying a catalyst for purification of exhaust gas also on the side of the electric heating type catalyst (H) means that the purification performance of the exhaust gas purification device (A) as a whole is improved, and as described above, the catalyst reaction does not occur. The effective amount of heat generation is based on this, and this heat generation amount is used to improve the heater characteristics. In the present invention, as the catalyst to be carried on the wall surface of the energization exothermic catalyst (H), an oxidation catalyst is preferable in view of the amount of heat generation as seen from the above-mentioned catalytic reaction, but oxidation reduction (three-way catalyst) (a three-way catalyst) -way catalyst). The method of supporting these catalyst components will be described later in the main catalyst (M).

In the present invention, the flat metal strip (1) used for producing the honeycomb body (H ₁ ) which constitutes the above-mentioned electric heating type catalyst (H) is an ordinary metal monolith type main catalyst. Strips used in the production of the carrier matrix, such as chrome steel (chrome 13-25%), Fe-Cr20
A band material having a thickness of 0.04 mm to 0.1 mm such as heat resistant stainless steel such as% -AI 5% or heat resistant stainless steel to which rare earth is added to improve the oxidation resistance is used. Also, as the corrugated strip (2), the flat strip (1)
Is used which is corrugated so as to have a predetermined substantially sine wave or trapezoidal wave. In addition, considering the electrical conductivity of the honeycomb body at high temperature, Ni-Cr alloy, Ni-Cr
-Fe alloy, Ni-Cr-Al-Fe alloy, etc. are also used. In particular, in the present invention, as described above, the exhaust gas purifying catalyst is used by being supported on the wall surface of the honeycomb body (H ₁ ) constituting the electric heating catalyst (H).
A member forming the honeycomb body (H ₁ ), that is, a flat strip material
(1) and corrugated strip (2) containing Al or having an Al layer provided on the surface thereof is heat-treated to give whisker-like or mushroom-like alumina (A
It is preferable that the l ₂ O ₃ ) layer is deposited. The above-mentioned whisker-like alumina contains Pt, Pd,
This is preferable because the washcoat layer for carrying the exhaust gas purifying catalyst such as Rh can be firmly held.

In the present invention, the electrode materials (B ₁ , B ₂ ) are arranged in the axial direction at the central portion and the outer peripheral portion of the honeycomb body (H ₁ ) which constitutes the above-mentioned electric heating type catalyst (H). It As such an electrode material (B ₁ , B ₂ ), one having a desired shape may be used according to the structure of the honeycomb body (H ₁ ). For example, as the electrode material (B ₁ , B ₂ ), a wire material such as heat resistant steel or nickel, a bar material, or a plate material is used. In the present invention, as the honeycomb body (H) having the heater function, a wound type honeycomb body is used by being fixed in a metal case (C ₁ ) as shown in FIGS. It goes without saying that the metal case (C ₁ ) may be used as the external electrode material (C = B ₂ ) because it is in a normal state. However, as described above, a separate electrode material (B ₂ ) can be used.

The arrangement relationship (electric connection) between the electric heating type catalyst (H) and the external power source section (4) of the present invention is as shown in FIG. 8 when viewed from the exhaust gas purifying apparatus (A) as a whole. If the catalyst (H) is centered, it may be carried out as shown in FIGS. In the present invention, although not shown, the power supply from the external power supply part (4) to the electrode materials (B ₁ , B ₂ ) may be performed by a timer for a limited time, or the desired power of the honeycomb body may be obtained. The temperature of the honeycomb body and the temperature of the exhaust gas may be measured by a sensor (thermocouple or the like) attached to the portion and turned on / off at a desired set value, and the mode is not limited in any way. .. 1 to 2 show on / off switching (7) of power supply. Further, although the DC power source is exemplified as the external power source unit (4), it goes without saying that it may be an AC power source as shown in other embodiments.

A second embodiment of the electric heating type catalyst (H) of the present invention will be described with reference to FIG. In the second embodiment shown in FIG. 3, the honeycomb body (H ₁ ) constituting the electric heating catalyst (H) is composed of two honeycomb bodies (H ₁ , H ₂ ). ₁ , H ₂ ) are arranged in series, and the structure of each is basically the same as that of the single honeycomb body (H ₁ ) shown in FIGS. However, the difference is that the width (l) of each honeycomb body (H ₁ , H ₂ ) is changed not linearly but nonlinearly (concave curve). Whether the width (l) of each honeycomb body is changed linearly or non-linearly depends on the manufacturing process of the honeycomb body.

A third embodiment of the electric heating type catalyst (H) of the present invention will be described with reference to FIG. The third embodiment is substantially the same as the second embodiment shown in FIG. 3, and two honeycomb bodies (H ₁ , H ₂ ) are arranged in parallel. In addition, in the third embodiment, the width of the honeycomb body is non-linear (convex curve shape).
In that the external metal material (C ₁ ) common to each honeycomb body is used as the external electrode material (B ₂ ).
It differs from that of the second embodiment.

A fourth embodiment of the electric heating catalyst (H) of the present invention will be described with reference to FIG. The fourth embodiment is substantially the same as the third embodiment shown in FIG. 4, except that the width (l) of the honeycomb body is changed non-linearly (stepwise), and The difference is that an AC power supply is used as the power supply section (4).

A fifth embodiment of the electric heating type catalyst (H) of the present invention will be described with reference to FIG. In the fifth embodiment, as the honeycomb body (H ₁ ) constituting the electric heating catalyst (H), _one having both end faces having a convex shape on the outer side is adopted, whereby the honeycomb body (H ₁ ) is exhausted. The width (l) in the gas flow direction is adjusted. The external power supply unit (4) is an AC power supply. In addition, in the fifth embodiment, the honeycomb body (H ₁ )
The shape has the advantage that the flow velocity distribution of the exhaust gas flow can be adjusted.

A sixth embodiment of the electric heating catalyst (H) of the present invention will be described with reference to FIG. In the sixth embodiment, as the honeycomb body (H ₁ ) constituting the electric heating catalyst (H), one having one end face convex outward and the other end face concave is adopted. The width (l) of the honeycomb body (H ₁ ) in the exhaust gas flow direction is adjusted. In the sixth embodiment as well, the flow velocity distribution of the exhaust gas flow can be adjusted as in the fifth embodiment.

As one use of the electric heating type catalyst (H) of the present invention, the function as a precatalyzer is emphasized, and the main catalyst which is the main constituent element of the exhaust gas purifying device (A) as described above. It is arranged and used in the front part of (M). Needless to say, the main catalyst (M) may be used in place of the main catalyst (M). Next, the main catalyst (M) will be described. The main catalyst (M), which is a main component of the exhaust gas purification device (A), may be a ceramic monolith type or a metal monolith type. These may be manufactured according to a conventional method, for example, a main catalyst supporting base material which is a precursor of the main catalyst (M) may be manufactured, and an exhaust gas purifying catalyst may be supported thereon. The method for producing the main catalyst-supporting base material of metal monolith type will be described below, but the honeycomb bodies (H _{1 to} H ₁ ) constituting the above-mentioned electric heating type catalyst (H) will be described.
_n ) may also be manufactured in the manner described below. In addition,
The method of supporting the catalyst will be described later.

The main catalyst carrier having a circular cross-section shown in FIG. 9 is constructed so that the heat-resistant thin metal plate flat plate strip (1) and corrugated strip strip (2) are in contact with each other. It is made by stacking and stacking them in a spiral shape. Multiple reticulated vent passages (cells) that become exhaust gas passages by winding lamination (3)
Is automatically formed. The above-mentioned winding type electric heating catalyst (H) is also manufactured by this method. More specifically, it may be manufactured as follows.
Fe-Cr 20% -Al 5% -Ce 0.02% heat-resistant steel thickness
A flat strip made of thin steel strip with a width of 0.04 mm and a width of 38 mm was passed between the forming gears, and pitch width (3.0 mm) and wave height (1.
4mm) corrugated strip material. Next, the flat plate-shaped strip and the corrugated strip-shaped strip are stacked on top of each other, and the end portion is inserted into the slit portion of the slit-formed roll forming rod, and the strips are collectively wound and laminated, for example, in a large number in the axial direction. Reticulated vent passage (cell density 300cps
The main catalyst-supporting base material made of metal and having an outer diameter of 70 mm and having i) may be used.

The main catalyst carrier having a circular cross section shown in FIG. 10 has a layer structure in which a flat band member (1) made of a heat-resistant thin metal plate and a corrugated plate member (2) are in contact with each other. It is made by stacking in a shape.

The main catalyst carrier having a circular cross-sectional shape shown in FIG. 11 is a purification element in which a flat band material (1) made of a heat-resistant thin metal plate and a corrugated plate material (2) are brought into contact with each other. (E), and the desired number of the purification element (E) is fixed shaft (S)
It is manufactured by radially extending from the starting point.

The main catalyst carrier having a circular cross section shown in FIG. 12 is made into a purification element (E) by bringing a heat-resistant thin metal plate flat plate-shaped strip and corrugated strip-shaped strip into contact with each other. The purification elements (E) are stacked in layers so that the outermost surface is a flat strip, and each purification element is centered on two fixed points (S ₁ , S ₂ ) set on the upper and lower outermost surfaces. (E) is bent in the opposite direction, that is, each purifying emellent (E) is bent into a substantially S-shaped curve.

In order to support the exhaust gas purifying catalyst such as Pt, Pd, and Rh on the main catalyst supporting base having various structures manufactured as described above, a usual method may be adopted. For example, first, the catalyst supporting layer for supporting the catalyst on the wall surface of the main catalyst supporting base material having the honeycomb structure is formed. To this, a slurry prepared by mixing activated alumina (r-Al ₂ O ₃ ) powder and alumina sol was applied,
Heat treatment may be performed at 0 ° C. Then, in order to support the catalyst such as Pt, Pd, and Rh catalyst on the catalyst supporting layer thus formed, a usual method such as impregnation treatment may be adopted to support the catalyst component. The main catalyst (M) is manufactured as described above.

The energized heat generation type catalyst (H) of the present invention is housed in a metal case (C) together with the main catalyst (M) described above for producing an exhaust gas purifying apparatus (A) as shown in FIG. It is fixed. Such a metal case (C)
Is for accommodating and fixing the above-mentioned energizing heat generating body catalyst (H) and the main catalyst (M) inside, and if the both ends are open, there is no restriction on their shape. is not. As the material of the metal case (C), heat-resistant steel of the same kind as the main catalyst-supporting base material may be used, or a material having high heat and corrosion resistance may be used. In addition, a double structure with the outer part of the metal material richer in heat resistance and corrosion resistance than the inner part, specifically, using the ferritic stainless steel for the inner part and the austenitic stainless steel for the outer part Good.

[0031]

The energizing heat-generating catalyst (H) of the present invention is a main constituent element (precatalyzer) of an exhaust gas purification apparatus.
Is used by being disposed upstream of the main catalyst (M) in the metal case (C), or as the main catalyst (M)
It is used instead of (as a main catalyzer). Then, the energization heat generation type catalyst (H)
Has a structure in which the temperature distribution is uniform inside and sufficient resistance heating is obtained, and further, an exhaust gas purifying catalyst is supported on the wall surface of the honeycomb body (H) to improve the heater characteristics. There is. Therefore, in the present invention, since the exhaust gas is uniformly heated in the electrothermal exothermic catalyst (H) and heated to a sufficiently high temperature suitable for the catalytic reaction, the exhaust gas treatment is particularly problematic at the time of cold start. The exhaust gas purification capacity can be greatly improved. Further, since the energization heat generation type catalyst (H) of the present invention carries the catalyst for purifying the exhaust gas on itself, the purifying performance of the entire exhaust gas purifying device (A) can be improved. Furthermore, in the electric heating catalyst of the present invention (H), the constituent members are not locally heated during heating,
It is possible to prevent the deterioration of vibration resistance durability (mechanical strength) due to member deterioration. Furthermore, since the catalyst (H) itself serves as a heater, it is not necessary to separately prepare and dispose a heater material.

[Brief description of drawings]

FIG. 1 is a sectional view in which a part of an electric heating catalyst (H) of a first embodiment of the present invention is omitted.

FIG. 2 is a perspective view of the electric heating type catalyst (H) shown in FIG.

FIG. 3 is a sectional view in which a part of an electric heating catalyst (H) according to a second embodiment of the present invention is omitted.

FIG. 4 is a sectional view in which a part of an electric heating catalyst (H) of a third embodiment of the present invention is omitted.

FIG. 5 is a sectional view in which a part of an electric heating type catalyst (H) of a fourth embodiment of the present invention is omitted.

FIG. 6 is a sectional view in which a part of an electric heating type catalyst (H) of a fifth embodiment of the present invention is omitted.

FIG. 7 is a sectional view in which a part of an electric heating type catalyst (H) according to a sixth embodiment of the present invention is omitted.

FIG. 8 is a cross-sectional view in which a part of a conventional exhaust gas purification device (A) is omitted.

FIG. 9 is a sectional view of a first embodiment of the main catalyst (M).

FIG. 10 is a sectional view of a second embodiment of the main catalyst (M).

FIG. 11 is a sectional view of a third embodiment of the main catalyst (M).

FIG. 12 is a sectional view of a fourth embodiment of the main catalyst (M).

[Explanation of symbols]

H ……… Electric heat generation type catalyst H ₁ , H _n …… Honeycomb body A ……… Exhaust gas purification device F ……… Exhaust gas flow direction B ₁ , B ₂ ……… Electrode material C ……… Exhaust gas Metallic case of purification device C ₁ ……… Metallic case of honeycomb body (H ₁ ) M ……… Main catalyst 1 ……… Flat plate strip 2 ……… Corrugated strip 3 ……… Cell ( Mesh-like vent hole) 4 ......... External power supply section 5, 6 ......... Lead wire

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location F01N 3/20 K 9150-3G 3/28 301 P 9150-3G

Claims (10)

[Claims] 1. An exhaust gas purifying apparatus comprising an energized exothermic catalyst (H) or a main catalyst disposed at the rear of the energized exothermic catalyst (H), wherein the energized exothermic catalyst (H) is i) A honeycomb-shaped structure manufactured by stacking flat plate-shaped strips made of thin metal plates and corrugated plate-shaped strips so as to be in contact with each other, and from the central part to the outer peripheral part of the honeycomb-shaped structure. The honeycomb body (H ₁ ) has a width (l) in which the width in the exhaust gas flow direction gradually decreases as it goes, and (ii) the honeycomb body (H ₁ ) functions as an exhaust gas purification catalyst. (3) Exhaust gas purification, characterized in that (iii) the honeycomb body (H ₁ ) is provided with an electrode material connected to an external power source in the central portion and the outer peripheral portion. apparatus. 2. A winding type in which a honeycomb body (H ₁ ) is laminated by stacking flat plate-shaped strips and corrugated plate-shaped strips so that they come into contact with each other, and spirally stacking them. The exhaust gas purifying apparatus according to claim 1, wherein Wherein the honeycomb body (H _1), is brought into contact with flat strip and the corrugated strip and purifying element, a desired number of the purifying element with radially by extension the fixed shaft starting The exhaust gas purifying apparatus according to claim 1, which is a manufactured radial type. 4. A honeycomb body (H ₁₎ is exhaust gas purifying apparatus according to claim 1 is intended to be divided into a plurality of honeycomb bodies (H ₁ ~H _n). 5. The exhaust gas purifying apparatus according to claim 1, wherein the honeycomb body (H ₁ ) is fixed in a metal case for the honeycomb body. 6. The exhaust gas purifying apparatus according to claim 1, wherein the width (l) of the honeycomb body (H ₁ ) changes linearly from the central portion to the outer peripheral portion. 7. The exhaust gas purifying apparatus according to claim 1, wherein the width (l) of the honeycomb body (H ₁ ) changes non-linearly from the central portion to the outer peripheral portion. 8. The exhaust gas purifying apparatus according to claim 5, wherein the metal case of the honeycomb body (H ₁ ) serves as an outer peripheral electrode material (B ₂ ). 9. The exhaust gas purifying apparatus according to claim 1, wherein the honeycomb body (H ₁ ) carries an oxidation catalyst for purifying exhaust gas. 10. The exhaust gas purifying apparatus according to claim 1, wherein the honeycomb body (H ₁ ) carries an oxidation-reduction catalyst for purifying exhaust gas.