The use of La1−xSrxFeO3 perovskite-type oxides as oxygen carriers in chemical-looping reforming of methane

Abstract La 1− x Sr x FeO 3 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 La 3+ by Sr 2+ is compensated by oxidation of a fraction of Fe 3+ to Fe 4+ 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 CO 2 and H 2 O because of its higher reactivity, while the other one prone to methane partial oxidation into H 2 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− x Sr x FeO 3 perovskites. An optimal range of the degree of Sr substitution is x  = 0.3–0.5 for La 1− x Sr x FeO 3 . 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.

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