Patent ID: 6182443
Filing Date: 2001-02-06
Classification: B01D,F01N,F02B,Y02A,Y02C,Y02T

Abstract:
An exhaust gas treatment system for diesel engine exhaust, said system comprising:a first catalyst component located in an exhaust gas passage of a diesel engine comprising a nitrogen oxide absorbent material upstream of a second catalyst component comprising a lean-NOx catalyst or a selective reduction catalyst, said nitrogen oxide absorbent material consisting essentially of:(a) a porous support material of alumina, and(b) at least 0.1 wt. % precious metal based on the weight of the porous support material selected from the group consisting of platinum, palladium, and rhodium, or a mixture of any of them;wherein said diesel exhaust gas flowing into said first catalyst component is always oxidizing and at low temperatures said porous support material of said first catalyst component absorbs nitrogen oxides from the exhaust gas through the catalytic effect of said precious metal and releases NOx gases at higher temperatures where they are converted to nitrogen or nitrous oxide over the second catalyst component.