No.sub.x reduction catalyst for internal combustion engine emission

Abstract

A system for reducing NO.sub.x gases found in the exhaust stream of the internal combustion engine is provided which includes an internal combustion engine having associated therewith a means for supplying fuel and oxygen to the engine, a manifold system for directing or channeling the exhaust gases from the engine, and an NO.sub.x reducing catalyst assembly communicating with the manifold which includes a housing having an NO.sub.x reducing catalytic structure of apertured thin metal foil positioned therein which comprises a durable, chromium containing corrosion resistant metal substrate having bonded thereto an effective amount of a NO.sub.x reducing catalyst selected from the group consisting of iron, nickel, cobalt, copper, manganese and mixtures thereof. In addition, an article composed of a catalytic material for reducing the oxides of nitrogen in exhaust gases from an internal combustion engine is also provided. The article includes a self-supporting catalytic structure in the form of an apertured, thin metal foil having a ratio of low mass to high surface area. In its preferred form, the foil is an expanded metal foil, and the article is formed by tightly winding the foil into a plural layer helical coil. The catalytic structure is produced by a method which comprises providing a thin sheet of metal foil, expanding the sheet of metal foil to thereby form a plurality of strands defining openings therebetween, depositing a metal on at least a part of the surface of the expanded metal foil which when alloyed with the metal foil increases its resistance to corrosion, alloying the deposited metal with the metal foil, and coating at least a part of the surface of the expanded metal foil with an adherent layer of a catalyst material which is capable of catalytically reducing the oxides of nitrogen (NO.sub.x) found in the exhaust gases emanating from an internal combustion engine.