The effect of the calcination temperature of LaFeO3 precursors on the properties and catalytic activity of perovskite in methane oxidation |
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Authors: | Barbara Kucharczyk Janina Okal Włodzimierz Tylus Juliusz Winiarski Bogdan Szczygieł |
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Affiliation: | 1. Faculty of Chemistry, Wroc?aw University of Science and Technology, Wybrze?e Wyspiańskiego 27, 50-370 Wroc?aw, Poland;2. Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 1410, 50-950 Wroc?aw, Poland |
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Abstract: | In the synthesis of perovskite-type LaFeO3 oxides iron and lanthanum nitrates were used as a precursors. The nitrates were dissolved in water, evaporated, crushed and calcined in temperature range of 650–850?°C. The obtained perovskites were applied as an active layer on monolithic catalysts for the oxidation of methane. The increase in the calcination temperature of the perovskite precursors from 650° to 850°C results in a reduction in the surface area of the powders from 10.1 to 4.2?m2/g. XRD studies revealed that calcination at 800–850?°C caused the formation of an almost homogeneous LaFeO3 perovskite phase. A decrease in the La/Fe surface ratio from 12 to 5.2 with the rise in calcination temperature from 650° to 800°C was detected by XPS. EDX results confirmed that at 750–850?°C, the La/Fe ratio in the perovskite layer is close to the stoichiometric and amount to 1.01–1.03. The highest activity in methane oxidation was achieved when the LaFeO3 perovskite was calcined at 700?°C. A further slight increase in the activity was noticed after H2 treatment. As the calcination temperature of the perovskites is increased, the catalyst activity decreases due to a reduction in the specific surface area, despite the more complete LaFeO3 perovskite phase formation. |
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Keywords: | Perovskites Calcination Chemical preparation Monolithic catalyst |
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