Automobile emission catalysts

摘要

A catalyst system includes a three-way catalyst (TWC) mounted underfloor and an engine management system programmed to initiate an enrichment of the exhaust gases exiting the engine with at least one of CO and hydrocarbons and to add secondary air to the exhaust gases in the exhaust passage upstream of the TWC. This periodic enrichment and addition of secondary air causes catalytic oxidation of the at least one of CO and hydrocarbons over the TWC thereby raising the underfloor TWC temperature to at least 550° C., preferably higher, in order to reduce sulphur poisoning of the catalyst and maintain the desired catalytic activity.