Pd Loading and Structure of Flame-Made Pd/YFeO3±δ

• Published in: Topics in catalysis 2015-10, Vol.58 (14-17), p.910-918
• Main Authors: Lu, Ye, Keav, Sylvain, Maegli, Alexandra E., Weidenkaff, Anke, Ferri, Davide
• Format: Article
• Language: English
• Subjects: Catalysis; Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Industrial Chemistry/Chemical Engineering; Original Paper; Pharmacy; Physical Chemistry
• ISSN: 1022-5528; 1572-9028
• DOI: 10.1007/s11244-015-0459-9

The interactions between a platinum-group metal (PGM) and a perovskite-type oxide are complex since the latter can accommodate the former in its structure, simply act as a support or, in specific cases, reversibly switch between these two behaviours, depending on the redox environment. Despite promising performances as oxidation catalysts, Y-based perovskite-type oxides are far less studied than their La-based counterparts and their interactions with PGM need to be better understood. The morphology, coordination and oxidation state of Pd species in Pd-doped YFeO 3±δ catalysts prepared by flame spray synthesis were investigated in dependence on Pd loading in the range of 0–2.5 wt%. Their thermal stability was assessed by calcination of the flame-made materials at 700 °C. Fresh and calcined samples were thoroughly characterized by STEM, N 2 -physisorption, XRD, XPS, DRIFTS and OSCC. Pd species were predominantly in the form of metallic nano-particles supported on YFeO 3±δ . The size of these nano-particles increased with increasing loading as evidenced by DRIFTS. XPS facilitated the identification of Pd 2+ species in strong interaction with the hexagonal YFeO 3 lattice, suggesting the partial incorporation of noble metal ions in the perovskite-type structure. After calcination at 700 °C, this contribution vanished in the catalysts containing at least 2 wt % Pd. The catalysts were tested for methane oxidation under stoichiometric conditions up to 850 °C. The catalyst with 2 wt% Pd exhibited the highest CH 4 oxidation activity. Reduction of the Pd content to 0.5 wt% resulted in the shift of the 50 % CH 4 conversion by only ca. 40 °C. Hence, flame-made Pd/YFeO 3±δ demonstrated to be a suitable material to maintain CH 4 conversion with reduced noble metal content.