Soot oxidation via CuO doped CeO2 catalysts prepared using coprecipitation and citrate acid complex-combustion synthesis

This work deals with soot oxidation under SO2 presence over CuO doped CeO2 prepared using two routes, coprecipitation (CP) and citrate acid complex-combustion synthesis (CA). TPO, XRD, BET, H2-TPR, O2-TPD, FTIR and XPS are utilized to correlate the performance and physicochemical features of catalysts. The results show that solid solutions are formed due to Cu2+ cations entering into the ceria lattice. This reorganization increases the amount of oxygen vacancies and then creates more surface active species (Ce4+/Ce3+ and O*), and increases the reducibility and oxygen storage capacity of catalysts, thus promoting catalytic activity for soot oxidation. Both for Cu0.05Ce0.95-CA and Cu0.05Ce0.95-CP after TPO in the presence of various concentrations of SO2, more Ce4+/Ce3+ redox couples, and more active oxygen species, detected by XPS technique and FTIR, respond to the better activity. When compared to Cu0.05Ce0.95-CP, the better reducibility and greater OSC, and active oxygen species of Cu0.05Ce0.95-CA coincide with its better activity. A possible pathway of soot oxidation over Cu0.05Ce0.95-CA is proposed, based on the relationship of the performance and the physicochemical features of catalysts, which pathway follows the mechanism associated with redox couple and oxygen spill over effect.