Method of using a low cost catalyst system

摘要

There is disclosed a method of using an exhaust gas catalyst for treatment of exhaust gases developed by burning a hydrocarbon based fuel in an internal combustion engine. These exhaust gases contain varying amounts of unburned hydrocarbons, carbon monoxide and oxides of nitrogen depending upon the operating conditions of the internal combustion engine. This specification teaches the use of an improved catalyst composition in which a support medium is provided for supporting the catalyst system, the support medium having an upstream support portion and a downstream support portion over which the exhaust gases pass in succession. The upstream support portion of the support medium has deposited thereon palladium and the downstream support portion of the support medium has deposited thereon palladium and tungsten. Tungsten is present on the downstream support portion of the support medium in a quantity such that tungsten is available to substantially all of the palladium on that portion of the support medium. The catalyst system has particular utility as a three-way catalyst operating at approximately stoichiometric conditions or as a catalyst for use in conjunction with the so-called "fast burn/low friction" engines or as an oxidation catalyst.