Preparation of alumina-supported Pd and LaMnO₃ catalysts with the site-selective deposition and their catalytic activity for NO-CO reaction

By the combination of the preparation techniques of intra-pore deposition of Pd and selective intra/extra-pore deposition of LaMnO₃, two types of alumina supported Pd-LaMnO₃ catalysts were successfully obtained. It was suggested from the reduction behavior of supported Pd-LaMnO₃ catalysts that when both Pd and LaMnO₃ coexisted in the alumina pores (Pd/LaMnO₃/Al₂O₃), Pd and LaMnO₃ existed in close proximity each other to appear the interaction and that when Pd and LaMnO₃ exist separately in and out of alumina pores, respectively (LaMnO₃out/Pd/Al₂O₃), the existing environment of Pd was similar to that in Pd/Al₂O₃. For NO-CO reaction, Pd/Al₂O₃ and LaMnO₃out/Pd/ Al₂O₃ showed comparable activity and N₂/N ₂O selectivity, and Pd/LaMnO₃/Al₂O₃ showed higher activity than and different N₂/N₂O selectivity from the two catalysts, revealing that the intimate Pd-LaMnO ₃ interaction is effective to modify the catalytic property of Pd species. The excellent catalytic property of Pd/LaMnO₃/Al ₂O₃ was sustained up to 800 °C of calcination temperature.