Structural characterisation of Ce_0.5Zr_0.5O₂ modified by redox treatments and evaluation for chlorinated VOC oxidation

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• 作者：Beatriz de Rivas^a ; Rub&#xe9 ; n Ló ; pez-Fonseca^a ; Miguel Á ; ngel Guti&#xe9 ; rrez-Ortiz^a ; Jos&#xe9 ; I. Guti&#xe9 ; rrez-Ortiz ; ^a ; ^{joseignacio.gutierrez@ehu.es}
• 关键词：Chlorinated VOCs ; Catalytic combustion ; Ce_0.5Zr_0.5O₂ mixed oxide ; Pyrochlores ; Redox aging
• 刊名：Applied Catalysis B: Environmental
• 出版年：2011
• 出版时间：14 January 2011
• 年：2011
• 卷：101
• 期：3-4
• 页码：317-325
• 全文大小：1100 K

文摘

In this work the application of a redox treatment consisting of a high-temperature reduction with 5 % H₂/Ar in the range 950–1075 °C for 0.5–3 h followed by mild oxidation at 550 °C with 5 % O₂/He was evaluated as a tool for improving the catalytic performance of Ce_0.5Zr_0.5O₂ mixed oxide in the combustion of chlorinated compounds. Structural, morphological and physico-chemical changes caused by the redox treatment were analysed by X-ray diffraction, Raman spectroscopy, BET measurements, NH₃-temperature programmed desorption, temperature programmed reduction with hydrogen, and oxygen chemisorption. Interestingly, after reduction at a temperature as high as 1050 °C during at least 1.5 h, a substantially enhanced redox behaviour was noticed which resulted in a significant promotion of the catalytic activity in comparison with the unmodified parent sample. Hence, the value of temperature of half conversion at 30,000 h⁻¹ decreased from 300 to 275 °C for the combustion of 1,2-dichloroethane, which was selected as a model chlorinated feed. This active performance was assigned to the formation of a new κ-CeZrO₄ phase after redox aging characterised by a markedly increased capacity of providing active oxygen species at low temperatures. For comparative purposes two additional Ce_0.5Zr_0.5O₂ samples calcined at 750 and 1000 °C were also characterised and catalytically tested.