Soot oxidation in low-O2 and O2-free environments by lanthanum-based perovskites: structural changes and the effect of Ag doping

The use of La-based, Cu (LCO), Mn (LMO) and Fe (LFO) perovskites doped with Ag was studied for potential application as cGPF soot oxidation catalysts. Special emphasis was placed on the effect of the soot, reaction gas composition, changes in rich/lean conditions and the resulting physicochemical changes in the catalyst and their reversibility. The use of a catalyst reduced the soot oxidation temperature significantly in a low-O2 environment and with Ag doping the soot oxidation temperature was decreased by 170 °C in loose contact and 230 °C in tight contact compared to uncatalyzed oxidation. For the soot oxidation in an O2-free environment, the highest oxygen storage capacity was found for LCO and LCAO (1 mol O per molcat). The release of such a high amount of O and reduction of Cu2+ to Cu0 was accompanied by the loss of perovskite structure (LCO → Cu/La2O3), which could be reversed following exposure to a high temperature low-O2 environment.