Removal of co, hydrocarbons and no.sub.x with catalyst containing

Abstract

A catalyst composition suitable for three-way conversion of internal combustion engine, e.g., automobile gasoline engine, exhaust gases includes a catalytic material disposed in on a carrier. The catalytic material contains a co-formed (e.g., co-precipitated) rare earth oxide-zirconia support on which a first rhodium catalytic component is dispersed, and an alumina support having a platinum catalytic component dispersed thereon. The catalytic material may also include a second rhodium catalytic component dispersed on the alumina support bearing the platinum or a second alumina support. The catalytic material may be disposed as a catalytic coating directly on the carrier or upon an optional undercoat which is disposed on the carrier and which includes alumina and optionally, ceria and/or, iron oxide. One or more of a metal oxide which is effective for the suppression of hydrogen sulfide emissions (such as bulk nickel oxide), thermal stabilizers such as alkaline earth oxides, rare earth oxides and zirconia may be dispersed throughout the catalytic coat and/or the undercoat. The present invention also provides a method for treating engine exhaust gases by contacting the gases under conversion conditions with the catalyst composition.