Low temperature NOx storage system for lean exhaust aftertreatment

An exhaust gas treatment system for treating a flowing NOx-containing and water-containing exhaust gas stream from a lean-burn, hydrocarbon-fueled engine, the system comprising:

• a multi-cylinder, reciprocating piston engine, operable under lean-burn conditions, and producing the flowing exhaust stream following engine-start and thereafter during engine operation, the exhaust gas stream being progressively heated from a relatively low temperature following an engine cold-start to a higher temperature following engine warm-up;
• an engine exhaust gas stream passage leading from the engine to a flow-through container of non-catalyzed absorbent particles, the non-catalyzed particles consisting of absorbent alumina particles;
• and an engine exhaust passage leading from the container of absorbent particles to a flow-through container of a selective reduction catalyst material for the reduction of NOx constituents in the exhaust gas stream;
• the selective reduction catalyst material requiring heat from the exhaust stream following a startup of the engine to increase the temperature of the reduction catalyst material to an operative temperature for the material;
• and
• the composition and amount of the contained absorbent particles being determined to temporarily absorb water and NOx from a relatively low temperature, flowing exhaust stream before the selective reduction catalyst has been heated by the warming exhaust gas, and the absorbent particles thereafter releasing absorbed water and NOx constituents into the higher temperature exhaust to be carried into contact with the selective reduction catalyst material.