Influence of hydrothermal aging on catalytic performance of α-Al2O3supported Pd-containing La0-9Sr0.1CoO3-δ oxides for CO-NO reaction

α-Al2O3-supported Pd-containing La0.9Sr0.1CoO3-δ oxides were prepared by impregnation and their catalytic performance for CO-NO reaction was measured. Compared with La0.9Sr0.1CoO3-δ/ α-Al2O3 (LaSrCo), the Pd-containing samples had higher catalytic activity, showing that Pd is the active component. Pd-doped sample (LaSrCoPd) showed good hydrothermal property and, compared with other samples, gave the best performance after hydrothermal aging. The fresh LaSrCo-supported Pd sample (Pd/LaSrCo) gave the best performance, but hydrothermal aging evidentLy reduced its activity, and its light-off temperature increased by 20°C after hydrothermal aging. In fresh Pd/LaSrCo sample, Pd ions existed as the form of PdO, while in fresh LaSrCoPd sample, Pd ions existed in the lattice of perovskite. During hydrothermal aging, near all of the Pd ions in bulk phase of perovskite were dislodged from the lattice and existed as the form of PdO particles. Small PdO particles agglomerated into large ones. The hydrothermal aging increased the amount of naked surface Pd ions of LaSrCoPd, but decreased that of Pd/LaSrCo.