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, and / or normal three-way catalytic
layers. 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 after forming its
reaction product with SOx 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.