The use of La_1?xSr_xFeO₃ perovskite-type oxides as oxygen carriers in chemical-looping reforming of methane

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• 作者：Fang He ; ^{hefang@ms.giec.ac.cn} ; Xinai Li ; Kun Zhao ; Zhen Huang ; Guoqiang Wei ; Haibin Li
• 关键词：Synthesis gas ; Chemical-looping reforming ; La1&minus ; xSrxFeO3 perovskites ; Oxygen carrier ; Methane
• 刊名：Fuel
• 出版年：2013
• 出版时间：June, 2013
• 年：2013
• 卷：108
• 期：Complete
• 页码：465-473
• 全文大小：798 K

文摘

La_1?xSr_xFeO₃ perovskite-type oxides with x = 0.1, 0.3, 0.5, and 0.9 were prepared by combustion method. The synthesized perovskites were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area, temperature-programmed reduction (TPR), and Fourier transformed infrared spectroscopy (FTIR). Pure phase of perovskite-type crystalline structure was obtained regardless of the degree of Sr substitution. TPR, FTIR, and XRD results suggests that the electronic unbalance caused by the partial substitution for La³⁺ by Sr²⁺ is compensated by oxidation of a fraction of Fe³⁺ to Fe⁴⁺ and/or generation of oxygen vacancies in the perovskite lattice. There exist two kinds of oxygen species on the oxides: surface absorption oxygen and bulk lattice oxygen. The surface oxygen contributed to oxidize methane completely to CO₂ and H₂O because of its higher reactivity, while the other one prone to methane partial oxidation into H₂ and CO. The activity of the substituted perovskites decreases as the degree of substitution x > 0.5. However, Sr substitution would inhibit methane decomposition in the methane reaction with La_1?xSr_xFeO₃ perovskites. An optimal range of the degree of Sr substitution is x = 0.3-0.5 for La_1?xSr_xFeO₃. The multicyclic redox reaction results indicated that the synthesized perovskite-type oxides have good regenerability, which is a very important performance required in chemical-looping reforming of methane.