The present invention relates to a layered catalyst composite useful for reducing
contaminants in exhaust gas streams, especially gaseous streams containing sulfur
oxide contaminants. More specifically, the present invention is concerned with
improved catalysts of the type generally referred to as "three-way conversion"
catalysts. The layered catalysts trap sulfur oxide contaminants which tend to poison
three-way conversion catalysts used to abate other pollutants in the stream. The
layered catalyst composites of the present invention have a sulfur oxide absorbing
layer before or above a nitrogen oxide absorbing layer. The layered catalyst composite
comprises a first layer and a second layer. The first layer comprises a first support
and at least one first platinum component. The second layer comprises a second
support and a SOx sorbent component having a free energy of formation
from about 0 to about -;90 Kcal/mole at 350 C. The sulfur oxide absorbing
layer selectively and reversibly absorbs sulfur oxides over nitrogen oxides and
prevents or alleviates sulfur oxide poisoning of the nitrogen oxide trap.
