The present invention relates to sulfur tolerant catalyst composites
useful for reducing contaminants in exhaust gas streams, especially
gaseous streams containing sulfur oxide contaminants. More specifically,
the present invention is concerned with improved NOx trap catalysts for
use in diesel engines as well as lean burn gasoline engines. The sulfur
tolerant NOx trap catalyst composites comprise a platinum component, a
support, a NOx sorbent component, and a spinel material prepared by
calcining as anionic clay material represented by the formula
M.sub.mN.sub.n(OH).sub.(2m+2n)A.sub.a.bH.sub.2O, wherein the formula is
defined herein. The sulfur tolerant NOx trap catalyst composites are
highly effective with a sulfur containing fuel by trapping sulfur oxide
contaminants which tend to poison conventional NOx trap catalysts used to
abate other pollutants in the stream. The sulfur tolerant NOx trap
catalyst composites are suitable for diesel engines because the
composites can be regenerated at moderate temperatures with rich pulses,
rather than at high temperatures.