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

La1-xSrxFeO3 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 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 La1-xSrxFeO3 perovskites. An optimal range of the degree of Sr substitution is x = 0.3-0.5 for La1-xSrxFeO3. 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. (C) 2012 Elsevier Ltd. All rights reserved.