Reactivity of La1 ? xSrxFeO3 ? y (x = 0–1) Perovskites in Oxidation Reactions |
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Authors: | L A Isupova I S Yakovleva G M Alikina V A Rogov and V A Sadykov |
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Institution: | (1) Boreskov Institute of Catalysis, Siberian Division, Russian Academy of Sciences, Novosibirsk, 630090, Russia |
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Abstract: | Oxygen species and their reactivity in La1 − x
Sr
x
FeO3 − y
perovskites prepared using mechanochemical activation were studied by temperature-programmed reduction (TPR) with hydrogen
and methane. The experimental data were compared with data on the catalytic activity in oxidation reactions. It was found
that the rates of CO and methane oxidation on the perovskites in the presence of gas-phase oxygen correlated (k = 0.8) with the amount of reactive surface oxygen species that were removed by TPR with hydrogen up to 250°C. Maximum amounts
of this oxygen species were released from two-phase samples (x = 0.3, 0.4, and 0.8), which exhibited an enhanced activity in the reaction of CO oxidation. In the absence of oxygen in the
gas phase, methane is oxidized by lattice oxygen. In this case, the process activity and selectivity depend on the mobility
of lattice oxygen, which is determined by the temperature, the degree of substitution, the degree of reduction, and the microstructure
of the oxide. Thus, the high mobility of oxygen, which is reached at high concentrations of point defects or interphase/domain
boundaries, is of importance for the process of deep oxidation. However, the process of partial oxidation occurs in single-phase
samples at low degrees of substitution (x = 0.1–0.2).
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Translated from Kinetika i Kataliz, Vol. 46, No. 5, 2005, pp. 773–779.
Original Russian Text Copyright ? 2005 by Isupova, Yakovleva, Alikina, Rogov, Sadykov. |
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Keywords: | |
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