Patent ID: 7922988

Claim:
An exhaust gas treatment system comprising: a catalytic material having the capability of simultaneously catalyzing the oxidation of hydrocarbons and carbon monoxide and the reduction of nitrogen oxides and having an upstream zone and a downstream zone deposited on a carrier; wherein in the upstream zone, the catalytic material comprises: an inner layer on the carrier, the inner layer comprising a support and a palladium component; an outer layer above the inner layer, the outer layer comprising a support and a rhodium component; and a first oxygen storage component located in the inner layer, the outer layer, or both; wherein in the downstream zone, the catalytic material comprises: an inner layer on the carrier, the inner layer comprising a support and a palladium component; an outer layer above the inner layer, the outer layer comprising a support and a rhodium component; and a second oxygen storage component located in the inner layer, the outer layer, or both such that the second oxygen storage component is present in an amount that is greater than the amount of the first oxygen storage component.