Abstract: A method for manufacturing a NOx absorbent useful to purge exhaust gases during lean-burn internal combustion engine operation. The material is resistant to sulfur poisoning hence improving the long term NOx absorption efficiency. The method comprises providing an alumina/ceria support with barium and precious metal of at least platinum and then overcoating with a layer of lithium. The absorbent can be used in the exhaust gas system and subjected to lean operation when the nitrogen oxides are absorbed and then to stoichiometric or rich A/F operation which causes the nitrogen oxide to desorb and then they are reduced over the precious metal.

Abstract: A method (100) and system (10) for controlling the temperature of a first NO.sub.x trap in an aftertreatment system for a variable displacement engine (12). The frequency of switching between first and second cylinder banks (14, 16) of said variable displacement engine (12) controls the temperature of the NO.sub.x trap (18) in order to maintain the temperature within a preferred operating temperature range. A set of control valves (V1, V2, V3) is used to direct the flow of exhaust from alternate cylinder banks (14, 16) through various paths in order to maintain the desired temperature of the first NO.sub.x trap (18). In another embodiment (30), the aftertreatment and method (120) include a second NO.sub.x trap (26) for situations in which both engine banks (14, 16) are run simultaneously.