In situ investigation of Diesel soot combustion over an AgMnOx catalyst

An AgMnOx catalyst (3.5 wt.% Ag) incorporating silver ions in a Mn2O3 phase exhibits high performances for soot oxidation below 300 °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 Mn2O3 → Mn3O4 → 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.

Graphical abstract.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► An AgMnOx oxide catalyst shows high activity for low temperature soot oxidation. ► Soot combustion under 18O2 forms preferentially C16O2 and C16O. ► The reaction follows a redox mechanism. ► Lattice oxygen transfer to the soot is responsible for ignition. ► Ag promotes Mn3+ reduction and Mn2+ oxidation.