NOx TRAP

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A NOx trap comprises components comprising at least one platinum group metal, at least one NOx storage material and bulk ceria or a bulk cerium-containing mixed oxide deposited uniformly in a first layer on a honeycombed substrate monolith, the uniformly deposited components in the first layer having a first, upstream, zone having increased activity relative to a second, downstream zone for oxidising hydrocarbons and carbon monoxide, and a second, downstream, zone having increased activity to generate heat during a desulphation event, relative to the first, upstream, zone, wherein the second, downstream, zone comprises a dispersion of rare earth oxide, wherein the rare earth oxide loading in gin-3 in the second, downstream zone is greater than the rare earth oxide loading in the first, upstream zone. An exhaust system for a lean burn internal combustion engine, a vehicle comprising a lean burn internal combustion engine and the exhaust system and methods of making the NOx trap according to the invention are also disclosed.