Compound Perovskite-type Oxygen Carrier For Synthesis Gas Production Via Chemical-looping Reforming Of Methane

Chemical-looping Reforming of Methane（CLDR）is a new type of synthesis gas generation technology that can convert CH₄into synthesis gas and activate the greenhouse gas CO₂through the circulation of oxygen carriers（OCs）.The key to CLDR is the OCs.The iron-based perovskite structure OCs are compatible with environment,which has the strong oxygen storage capacity and the reserves is abundant.Cerium oxide has strong oxygen release and oxygen carrying capacity in the redox process.Therefore,in this paper,the composite of cerium oxide and iron-based perovskite-type La_0.6Sr_0.4FeO₃OC is used to prepare syngas in CLDR,combining characterization methods such as XRD,H₂-TPR and XPS to explore the internal mechanism of between the microstructure of OCs and the reaction CLDR.It is also investigated that the calcination temperature and Al doping how to affect the redox performance of the composite perovskite OCs:1.Based on La_0.6Sr_0.4FeO₃,the effect in the mass of loading cerium on the structure of La_0.6Sr_0.4FeO₃OCs and CLDR reaction performance was investigated.It was found that the loading of cerium caused the oxygen carrier to form a coexisting structure of Ce₄O₇(Ce³⁺and Ce⁴⁺coexisting)and perovskite La_0.6Sr_0.4FeO₃.As the cerium loading increases,the grain size of the perovskite OCs becomes larger.Molarby is Ce:Fe:3:7,and the Ce₄O₇-La_0.6Sr_0.4FeO₃composite oxygen carrier has good cycle stability after 10 CH₄/CO₂redox cycles.2.The effects of different calcination temperatures（800-1100 ℃）on the microstructure and CLDR reaction performance of Ce₄O₇-La_0.6Sr_0.4FeO₃were investigated.It was found that different calcination temperatures did not significantly affect the phase composition of the composite perovskite OCs,but changed the structural parameters of the composite perovskite OCs,which in turn affected the CLDR reaction performance of the composite perovskite OCs.The Ce₄O₇-La_0.6Sr_0.4FeO₃-1000℃ OC still maintains relatively high activity and stability during the CH₄/CO₂redox process due to its rich lattice oxygen content and high rate.3.The effect of Al incorporation on the microstructure and CLDR reaction performance of the composite perovskite OCs were investigated.It was studied that Al-mixed zircoxide did not exist in the form of Ce₄O₇but in the form of Ce O₂.In addition,a La_0.6Sr_0.4Fe_xAl_1-xO₃solid solution structure was formed.The Al-mixed also affects the structural parameters of the composite perovskite OCs and further affects the CLDR reaction performance of the composite perovskite OC.Ce O₂/La_0.6Sr_0.4Fe_xAl_1-xO₃OCs with Al’s Molar ratio of Ce:Fe:Al:3:7:2 show excellent oxygen migration and good methane selective oxidation.A proper amount of Al doping improves the anti-sintering performance of the OCs,and the structure and reactivity of the composite OCs can be kept stable after ten CH₄/CO₂ redox cycles.