Patent ID: 7562522

Claim:
A diesel engine exhaust aftertreatment system, comprising: a lean NOx trap comprising an effective amount of NO x adsorbent selected from the group consisting of alkali and alkaline earth metal compounds to adsorb and store NOx from lean exhaust and adapted to reduce and release the stored NOx under rich exhaust conditions; an ammonia-SCR catalyst configured to receive gases released from the lean NOx trap and functional to catalyze a reaction with ammonia that can reduce NOx in a lean environment; and an additional catalyst, configured between the lean NOx trap and the ammonia-SCR catalyst, the additional catalyst comprising: a) an effective amount of one or more supported transition metals functional to catalyze reactions between NO x and hydrocarbons under rich conditions whereby the additional catalyst is functional mitigate poisoning of the ammonia-SCR catalyst by hydrocarbons during LNT regeneration by catalyzing reactions between NO x and hydrocarbons under rich conditions; b) an effective amount of oxidation catalyst and an effective amount of oxygen-storing material, whereby the additional catalyst is functional to mitigate poisoning of the ammonia-SCR catalyst during LNT regeneration by oxidizing hydrocarbons under rich conditions using oxygen stored by the additional catalyst; or c) an effective amount of a hydrocarbon adsorbant, whereby the additional catalyst is functional to mitigate poisoning of the ammonia-SCR catalyst by hydrocarbons during LNT regeneration by adsorbing hydrocarbons under rich conditions; wherein the lean NOx trap is functional to generate ammonia under rich exhaust conditions and the ammonia-SCR catalyst is functional to adsorb most of the ammonia so generated; the ammonia-SCR catalyst is functional to reduce NOx passing the lean NOx trap by catalyzing a reaction of NOx with the adsorbed ammonia; and the additional catalyst is functional to mitigate poisoning of the ammonia-SCR catalyst by hydrocarbons.