Field of the Invention
The invention relates to a catalytic converter and a method for producing the same.
Typical catalytic converters of the kind which are used, for instance, to reduce the nitrogen oxides in flue gas, usually include a metal carrier body, an adhesion-promoting intermediate layer, and a catalytically active layer applied to the intermediate layer. In the manufacture of catalytic converters, a fundamental problem which arises is that of establishing good adhesion of the catalytically active layer to the metal carrier body.
Particularly for producing plate-type catalytic converters, methods for solving that problem are known in which an adhesion-promoting intermediate layer is produced on an expanded metal carrier body (U.S. Pat. Nos. 4,370,262; 4,285,838 and 4,455,281) by spraying on liquid aluminum (aluminum flame spraying). However, producing a catalytic converter with that method requires that a very large amount of energy be expended to liquefy the aluminum. Moreover, liquid aluminum, which drops through voids in the carrier body during the spraying process, is no longer directly reusable, because some of it is oxidized. Both of those situations make such a method relatively expensive.
Published European Application No. 0 387 394 A1 also discloses a method in which the carrier body of the catalytic converter is produced by sintering from multiple-ply fabrics and/or from knitted goods and/or from fibrous material. A disadvantage of that method is that fabrics and knitted goods are complicated and expensive to produce, while conversely fibrous materials can be produced only in a relatively poorly defined form.
It is accordingly an object of the invention to provide a catalytic converter and a method for producing the same, which overcome the hereinafore-mentioned disadvantages of the heretofore-known devices and methods of this general type, with which a catalytic converter, in particular a plate-type catalytic converter, can be produced economically and in which good adhesion of the catalytically active layer to the metal carrier body is achieved at the same time.