Well-defined Ln2Sn2O7 powders (Ln = La, Sm and Gd) with a phase-pure pyrochlore structure were synthesized by hydrothermal reaction. The catalytic activities of Ln2Sn 2O7 powders for methane combustion were measured. Methane oxidation started at 500°C and increased with oxidation temperature. Catalytic methane combustion is strongly influenced by the presence of oxygen vacancies that form by breaking Sn-O lattice bonds as the temperature increases. Addition of manganese to the rare earth pyrochlores improved methane oxidation activity. Manganese-doped samarium stannate pyrochlore (Sm2Sn 1.8Mn0.2O7 shows highest the catalytic activity. Light-off and complete oxidation temperatures were measured at about 400 and 650°C, respectively.
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