Patent ID: 8112987
Filing Date: 2012-02-14
Classification: B01D,F01N,Y02A,Y02T

Abstract:
1. A method of reducing NOx emissions from an engine exhaust, the method comprising: a) flowing a lean exhaust through a first lean NOx trap such that exhaust emerging from the first lean NOx trap flows through an SCR catalyst system; b) flowing the lean exhaust through a second lean NOx trap such that exhaust emerging from the second lean NOx trap flows through the SCR catalyst system; c) limiting the flow through the first lean NOx trap when NOx slippage through the first lean NOx trap is greater than a first predetermined slippage value; d) providing a reductant to the first lean NOx trap in a sufficient amount to generate ammonia from the first lean NOx trap when NOx slippage from the second NOx trap is greater than a second predetermined slippage value; and e) directing the ammonia from step d) to the SCR catalyst system wherein the ammonia and the exhaust emerging from the second lean NOx trap in step b) contact the SCR catalyst system substantially contemporaneously.