Exhaust system for lean burn IC engines

An exhaust system for a lean-burn internal combustion engine, comprising:

• a nitrogen oxide (NOx) absorbent;
• a first catalyst for catalysing the selective catalytic reduction (SCR) of NOx with a NOx-specific reactant disposed upstream of the NOx absorbent;
• first means for introducing a NOx-specific reactant, or a precursor thereof, into an exhaust gas upstream of the first catalyst;
• and
• means for controlling the introduction of the NOx-specific reactant, or the precursor thereof, into the exhaust gas via the first introducing means, wherein the means for controlling:
• (a) causes the introduction of a first amount of NOx-specific reactant, or the precursor thereof, to contact the NOx absorbent insufficient to completely reduce the total NOx stored on the NOx absorbent when the first catalyst is inactive for reducing NOx to N2;
• and
• (b) causes the introduction of a second amount of NOx-specific reactant, or the precursor thereof, to contact the first catalyst when the first catalyst is active for reducing NOx to N2, wherein the second amount of NOx-specific reactant is of a sufficient amount such that NOx-specific reactant slips the first catalyst and contacts the NOx absorbent to reduce the NOx stored on the NOx absorbent and regenerate the NOx absorbent.