Iron-Doped CaTiO 3 and Pd/YSZ Dual Bed Catalytic System for CH 4 Emission Control from Natural Gas Vehicle

The catalytic treatment of residual traces of refractory methane in the exhaust gas from NGV engines involves the use of expensive, highly loaded precious metal based catalysts. Recently, it was demonstrated that the association of a perovskite with a Pd/YSZ (Yttria-stabilized zirconia) catalyst improved both the oxygen exchange behavior on the YSZ support together with the methane oxidation on palladium. However, these interesting results were obtained in condition quite far from an exhaust pipe and this work aims to investigate the concept of this dual catalytic bed system in more realistic conditions. In this study, a mixed electronic/ionic conducting perovskite (CaTi 0.7 Fe 0.3 O 3-δ ) was associated to a pure oxygen ion conductor (YSZ) impregnated with 1% palladium. This dual-bed configuration promoted CH 4 abatement in lean mixture, probably associated to the Pd/PdO active phase formation, but inhibiting effect of both CO 2 and H 2 O was also observed.