Abstract
Perovskite-type oxides could be applied for chemical looping steam methane reforming (CL-SMR) with a high selectivity in reacting with methane, but the reaction capacity is relative low. The supports with a high oxygen capacity could enhance the relative low reaction capacity of perovskite and improve the reaction selectivity. In this study, CeO2-supported Ba1-xSrxCoO3-δ perovskite with different A-site doping ratios (x = 0, 0.1, 0.3, 0.5, 0.7, 0.9) were synthesized by sol-gel method, and the reactivity and cyclic performance of Ba1-xSrxCoO3-δ/CeO2 were analyzed. The Sr-doping Ba1-xSrxCoO3-δ/CeO2 oxygen carrier had a higher gas production than non-doping BaCoO3-δ/CeO2, and the Ba0.3Sr0.7CoO3-δ/CeO2 showed the highest gas productions among the six samples. Sr-doping in A-site of perovskite increased the amounts of syngas and hydrogen, H2/CO ratio of syngas production was closed to the ideal value. XRD, XPS and FESEM were employed to investigate the physical and chemical properties of Ba1-xSrxCoO3-δ/CeO2. The XRD results suggested that a part of CeO2 reacted with A-site elements of perovskite and converted to BaCeO3 and SrCeO3. Ce ion reversibly shuttle between CeO2 and ACeO3 (A = Ba, Sr) depending on the local redox condition, this synergistic effect of A-site element and CeO2 not only enhanced the selectivity of partial oxidizing of methane, but also increased the gas production of syngas and hydrogen compared with pure CeO2 and Ba1-xSrxCoO3-δ. XPS results indicated that lattice oxygen was the main oxygen source for syngas production. Moreover, Ba1-xSrxCoO3-δ layer could get oxygen supply from CeO2 and increase the gas production. FESEM showed that the uniformly adhered perovskite particles on the surface of CeO2 could get more oxygen supply of CeO2 to enhance gas productions; the slightly aggregation of Ba1-xSrxCoO3-δ perovskite could enhance the oxygen mobility and improve the cyclic performance of Ba1-xSrxCoO3-δ/CeO2.
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