Pd substitution effects on perovskite catalyst activity for methane emission control

Abstract

Perovskite-type oxides of the LaBO 3 and LaB 0.9Pd 0.1O 3 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, LaBO 3, 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 LaMn 0.9Pd 0.1O 3 catalyst was 425 °C, compared to 485 °C for LaMnO 3, with a W/F = 0.12 g s/cm 3. On the basis of a Temperature Programmed Desorption (TPD) analysis of oxygen as well as catalytic combustion runs, the prevalent activity of the LaMn 0.9Pd 0.1O 3 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-Al 2O 3 supported form (catalyst weight percentage 15%) and tested in a lab-scale test rig under realistic conditions. Half methane conversion ( T 50) was achieved at 340 °C (Gas Hourly Space Velocity (GHSV) = 10 000 h −1), almost the same T 50 value as the commercial 4 wt% Pd/γ-Al 2O 3 catalyst, but with a six-times lower amount of the expensive noble metal.