Exhaust emission purifying device and method for an internal combustion engine

Emission cleaning device for the exhaust gases of an internal combustion engine (1) with a storage reduction type NOx catalyst (50a) which is able to store NOx, a reducing agent supply (20) for supplying reducing agent to the storage reduction type NOx catalyst (50a) and an electronic control unit (22) for controlling the reducing agent supply (20), wherein the storage reduction type NOx catalyst (50a) capable of storing not only NOx but also SOx, which reduces the absorption of NOx and to poisoning of the storage-reduction type NOx catalyst (50a) leads, which can be removed by a recovery process with supply of reducing agents, wherein when the storage reduction type NOx catalyst (50a) is still in a post-treatment phase, in the noble metal compounds of the storage reduction type NOx catalyst (50a) in contact contact and chemically stabilized, the electronic control unit (22) d ie timing for carrying out a recovery process for controlling the start time and the duration of the recovery process on the basis of past operation data of the internal combustion engine (1) determines.