Soot combustion over silver-supported catalysts

In this study the characterization and soot oxidation activity of Ag-based catalysts deposited on alumina, ceria and zirconia have been investigated. The combustion of soot was shown to be promoted by the presence of silver, especially in a zero valent state, over all the supports investigated. Presence of silver in a positive oxidation state is favoured with CeO(2), while zero valent silver dominates over alumina and zirconia. This is likely attributed to the oxygen storage capacity of ceria which stabilizes silver in an oxidized form. Soot oxidation starts at low temperature (around 500 K for Ag on ZrO(2)) with a T(50) in the range of 600-640 K. Deactivation under strong ageing conditions (1023 K for 12 h) is negligible with alumina and zirconia, while in the presence of ceria, which slows down formation of metallic silver from Ag(2)O, loss of activity following thermal treatments at high temperatures becomes more intense.