The storage of NOx under lean conditions in model NOx storage catalysts as
well as the deactivation by sulphur have been studied. We find that NO2 pla
ys an important role in the storage mechanism as an oxidising agent. Two di
fferent mechanisms for this are discussed: the formation of surface peroxid
es and the oxidation of nitrites to nitrates, FTIR studies show that NOx is
stored as surface nitrates, The sulphur deactivation is found to be more s
evere when SO2 is added during the rich phase than when SO2 is added during
the lean period. FTIR shows the formation of bulk sulphates both under lea
n and rich conditions.