Pd substitution effects on perovskite catalyst activity for methane emission control

Perovskite-type oxides of the LaBO3 and LaB0.9Pd0.1O3 series (where B = Cr, Mn, Fe) have been prepared and characterized by X-ray diffraction (XRD), BET specific surface area, and field emission scanning electron microscope (FESEM) techniques. The activity of the reference perovskites, LaBO3, and the new versions (with Pd introduction at the B-site) towards the combustion of methane, was evaluated in a Temperature Programmed Combustion (TPC) apparatus. Perovskite-type oxide containing Mn and Pd at the B-site was found to provide the best results. The half-conversion temperature of methane over the LaMn0.9Pd0.1O3 catalyst was 425 °C, compared to 485 °C for LaMnO3, with a W/F = 0.12 g s/cm3. On the basis of a Temperature Programmed Desorption (TPD) analysis of oxygen as well as catalytic combustion runs, the prevalent activity of the LaMn0.9Pd0.1O3 catalyst could be explained by its capability to deliver a higher amount of intrafacial oxygen. This catalyst was then deposited on cordierite monoliths in a γ-Al2O3 supported form (catalyst weight percentage 15%) and tested in a lab-scale test rig under realistic conditions. Half methane conversion (T50) was achieved at 340 °C (Gas Hourly Space Velocity (GHSV) = 10 000 h−1), almost the same T50 value as the commercial 4 wt% Pd/γ-Al2O3 catalyst, but with a six-times lower amount of the expensive noble metal.