An AgMnO
x catalyst (3.5 wt.%Ag) incorporating silver ions in a Mn
2O
3 phase exhibits high performances for
soot oxidation below 300 掳C. Its structural and redox properties have been investigated under reaction conditions using in situ XRD and DTA-TGA measurements. The catalyst appears unmodified during
soot combustion experiments under oxygen, but in the absence of oxygen the
soot is stoichiometrically oxidised by lattice oxygen leading to catalyst bulk reduction according to the steps Mn
2O
3 鈫?#xA0;Mn
3O
4 鈫?#xA0;MnO.
The isotopic reaction product composition (C16O2, C18O16O, C16O2, C16O and C18O) obtained during soot combustion experiments under 18O2 reveals that the reaction follows a redox mechanism, in which the transfer of lattice oxygen from the catalyst to the soot is responsible for the soot ignition at low temperature.