Pd-Integrated Perovskite as Effective Catalyst for Selective Catalytic Reduction of NOx by Propene
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Perovskite based Pd catalysts were prepared by a modified citrate route and analyzed with SEM, XRD, TEM and XPS techniques regarding the state of palladium. Integration of Pd into the perovskite lattice was compared with impregnation onto the support. Clear indications of Pd-substitution in the La-based perovskites were found by XPS and SEM. The integrated Pd-ions diffuse out of the perovskite lattice under reductive conditions forming metallic palladium nano-particles (less than 15 nm size) while the Pd particles obtained via the impregnation route were in the order of 80 nm. In the selective catalytic reduction of NO by propene, up to 35% NO conversion at 250 °C were obtained at a very low W/F of 0.015 g s mL−1, with decreasing tendency at increasing oxygen content. Differences between impregnated and Pd-integrated catalysts were obvious only at high O2 content (5 vol.%) where the Pd-integrated catalyst exhibited a lower tendency to oxidize the propene reductant.
KeywordsPd-integrated perovskites SCR of NO Propene
We gratefully acknowledge funding provided by German Research Foundation (DFG) in the frame of SPP 1299 (grants No. SA 1343/5-1 and GR 1447/17-1). We are grateful for the painstaking TEM-work of Dr. Klemens Kelm of the DLR-Institute of Materials Research for the analysis of the Pd-state in the perovskites.