Study of Lanthanum Manganate and Yttrium-Stabilized Zirconia-Supported Palladium Dual-Bed Catalyst System for the Total Oxidation of Methane: A Study by 18O2/16O2 Isotopic Exchange

• Published in: ChemCatChem 2016-06, Vol.8 (11), p.1921-1928
• Main Authors: Richard, Mélissandre, Can, Fabien, Gil, Sonia, Giroir-Fendler, Anne, Duprez, Daniel, Bion, Nicolas
• Format: Article
• Language: English
• Subjects: heterogeneous catalysis; hydrocarbons; isotopic labeling; oxidation; perovskite
• ISSN: 1867-3880; 1867-3899
• DOI: 10.1002/cctc.201501398

A significant enhancement of the yttrium‐stabilized zirconia‐supported palladium (0.2 wt % Pd/YSZ) catalytic activity for the total oxidation of methane was achieved in a dual‐bed system by the association of LaMnO3+Pd/YSZ materials. The combination with the best performance was 40 wt % LaMnO3+60 wt % Pd/YSZ. Pd/YSZ and LaMnO3 perovskite were characterized by using the 18O2 exchange technique. A Mars–van Krevelen mechanism was demonstrated over Pd/YSZ at 425 °C. Additionally, it was evidenced that LaMnO3 activated the O2 molecule on the YSZ oxygen vacancy sites to result in a significant increase of the oxidation rate characterized by a correlating decrease of the light‐off temperature of 65 °C. It takes two: The dual LaMnO3 yttrium‐stabilized zirconia‐supported (YSZ) metal catalytic system is highly active if the metal is 0.2 wt % Pd for CH4 combustion at moderate temperatures. However, the performance depends on the proportions of LaMnO3 and YSZ in the dual‐bed composition. The role of LaMnO3 is to generate active singlet oxygen species to improve the oxygen activation step on the YSZ surface. The rate of the oxidation of methane, which followed a Mars–van Krevelen mechanism, is then increased drastically.