Apparatus comprising lean burn ic engine and an exhaust system therefor

A method of desulfating a NOx adsorber catalyst (NAC) in an exhaust system of a lean burn internal combustion engine comprising a first substrate monolith comprising a NO adsorber catalyst (NAC);

• and a catalysed soot filter (CSF) comprising a filter substrate, which method comprising the steps of:
• (i) contacting sulfated NAC with enriched exhaust gas for a time and at a temperature sufficient to desorb sulfur-containing species adsorbed thereon, thereby to generate hydrogen sulfide;
• and
• (ii) contacting exhaust gas containing hydrogen sulfide with a compound effective to remove and/or convert at least some hydrogen sulfide from the rich exhaust gas,
• wherein at least some of the compound effective to remove and/or convert at least some hydrogen sulfide from the exhaust gas is disposed downstream of the NAC.