Patent ID: 8225600

Claim:
A method for remediating a NOx-containing lean diesel emission having a direction of flow, the method comprising the steps of: (a) providing a LNT/SCR catalyst system including a SCR catalyst, a first LNT having a first NOx storage capacity, and a second LNT having a second NOx storage capacity, the second LNT being disposed downstream of the first LNT relative to the direction of flow of the NOx-containing lean diesel emission, having a downstream exit from the second LNT, and fluidly communicating with the first LNT, the SCR catalyst being disposed downstream of and fluidly communicating with the second LNT, the SCR catalyst being capable of communicating with the first LNT, the second LNT having a portion of absorbed NOx; (b) introducing the lean NOx-containing diesel emission to the first LNT; (c) absorbing at least a portion of the NOx from the NOx-containing lean diesel emission on the first LNT to form a substantially NOx-free, lean diesel emission exiting downstream from the first LNT; (d) introducing an exotherm generating agent (EGA) for an EGA introduction time period into the substantially NOx-free lean diesel emission between the first LNT and the second LNT to form a reactive lean diesel emission; (e) introducing the reactive lean diesel emission to the second LNT generating a quantity of heat effective for desorbing a portion of absorbed NOx from the second LNT to form a lean, desorbed NOx emission; (f) streaming the lean, desorbed NOx emission downstream from the exit of the second LNT; (g) introducing a reducing agent (RA) for an RA introduction time period into the lean, desorbed NOx diesel emission between the second LNT and the SCR catalyst; and (h) remediating the lean, desorbed NOx diesel emission in the SCR catalyst to obtain the remediated diesel emission.