Patent ID: 7329629
Filing Date: 2008-02-12
Classification: B01D,B01J,Y02T

Abstract:
1. A catalyst system for use in reducing emissions from an exhaust gas stream containing hydrocarbons, CO and NOx comprising: a first lean NOx trapping catalyst for optimizing the storage of NOx emissions under lean air/fuel ratios, comprising a first zone and a second zone, wherein the entire first zone is positioned upstream of the second zone; said first zone comprising a) a catalyst mixture PM-Rh, where PM is a catalyst material selected from the group consisting of Pt, Pd and combinations thereof, and b) a metal oxide selected from the group consisting of oxides of aluminum, alkali metals, alkaline-earth metals, and combinations thereof, wherein said first zone is devoid of cerium; said second zone comprising a) a catalyst mixture PM-Rh, where PM is a catalyst material selected from the group consisting of Pt, Pd and combinations thereof, and b) a metal oxide selected from the group consisting of alkali metals, alkaline earth metals, rare earth metals and combinations thereof; and a second catalyst for optimizing the reduction of hydrocarbon, NOx and CO emissions under stoichiometric air/fuel ratios comprising: a) a catalyst mixture PM-Rh, where PM is a catalyst material selected from the group consisting of Pt, Pd and combinations thereof, b) a metal oxide selected from the group consisting of oxides of aluminum, alkali metals, alkaline earth metals and combinations thereof, and c) a metal oxide selected from the group consisting of oxides of zirconium, cerium and combinations thereof.