Deactivation Study of Fe2O3–CeO2 during Redox Cycles for CO Production from CO2

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• 作者：N. V. R. Aditya Dharanipragada ; Maria Meledina ; Vladimir V. Galvita ; Hilde Poelman ; Stuart Turner ; Gustaaf Van Tendeloo ; Christophe Detavernier ; Guy B. Marin
• 刊名：Industrial & Engineering Chemistry Research
• 出版年：2016
• 出版时间：May 25, 2016
• 年：2016
• 卷：55
• 期：20
• 页码：5911-5922
• 全文大小：605K
• 年卷期：0
• ISSN：1520-5045

文摘

Deactivation was investigated in Fe₂O₃–CeO₂ oxygen storage materials during repeated H₂-reduction and CO₂-reoxidation. In situ XRD, XAS, and TEM were used to identify phases, crystallite sizes, and morphological changes upon cycling operation. The effect of redox cycling was investigated both in Fe-rich (80 wt % Fe₂O₃–CeO₂) and Ce-rich (10 wt %Fe₂O₃–CeO₂) materials. The former consisted of 100 nm Fe₂O₃ particles decorated with 5–10 nm Ce_1–xFe_xO_2−x. The latter presented CeO₂ with incorporated Fe, i.e. a solid solution of Ce_1–xFe_xO_2−x, as the main oxygen carrier. By modeling the EXAFS Ce–K signal for as-prepared 10 wt %Fe₂O₃–CeO₂, the amount of Fe in CeO₂ was determined as 21 mol %, corresponding to 86% of the total iron content. Sintering and solid–solid transformations, the latter including both new phase formation and element segregation, were identified as deactivation pathways upon redox cycling. In Ce-rich material, perovskite (CeFeO₃) was identified by XRD. This phase remained inert during reduction and reoxidation, resulting in an overall lower oxygen storage capacity. Further, Fe segregated from the solid solution, thereby decreasing its reducibility. In addition, an increase in crystallite size occurred for all phases. In Fe-rich material, sintering is the main deactivation pathway, although Fe segregation from the solid solution and perovskite formation cannot be excluded.