Properties Of Lanthanum-based Perovskite Oxygen Carriers In Chemical Chain CH₄ Reforming Coupled To CO₂ Reaction

Chemical looping reforming of methane coupled with carbon dioxide decomposition process is a novel technology that can simultaneously produc e syngas and utilize CO₂.In this technique,methane is first partially oxidized to syngas（H₂+CO）by the lattice oxygen of the oxygen carrier.Subsequently,the reduced oxygen carrier recovers the missed lattice oxygen from the CO₂,and simultaneously produces CO.The design and construction of oxygen carriers with high activity and stability is the key factor to realize this technology.La-based perovskite oxides can be used as oxygen carriers for Chemical looping reforming of methane technology due to their unique structural properties and excellent oxygen storage and release properties.In this paper,Ce and Ni doped the series of La-Ce-Fe-Ni-O perovskite oxygen carriers were successfully prepared by the sol-gel method.The physical and chemical properties of oxygen carriers were characterized by XRD,BET,XPS and T PR.The reactivity of Chemical looping reforming of methane coupled with carbon dioxide decomposition process over the series of La-Ce-Fe-Ni-O oxygen carriers was systematically investigated.In addition,the influence of Ce/Ni doped amount and calcination temperature on the reactivity of oxygen carriers was further explored.LaFeO₃ was used as an oxygen carrier for the Chemical looping reforming of methane coupled with carbon dioxide decomposition process.It owned a high oxygen storage and release performance,but poor carbon deposition resistance,leading to a lower CH₄ conversion.The series of La-Ce-Fe-Ni-O oxygen carriers exhibited good oxygen transport capacity and high reactivity during the process.With the increase of Ce/Ni doped content,the CH₄ reactivity of the series of La-Ce-Fe-Ni-O oxygen carriers also gradually increased.La_0.6Ce_0.4Fe_0.6Ni_0.4O₃ sample exhibited the highest CO selectivity,syngas productivity and H₂ productivity,and its H₂/CO molar ratio was close to the ideal ratio of 2.0（1.0-1.6）during the whole process.During the 20 redox cycles,it maintained a good CH₄ reactivity,structural stability and thermal stability.The effect of calcination temperature on structure properties of the La_0.6Ce_0.4Fe_0.6Ni_0.4O₃was investigated in detail.It was found that the samples calcined at 800 ^oC exhibited higher concentration of oxygen vacancies and better oxygen storage and release performance.During the 20 redox cycles,La_0.6Ce_0.4Fe_0.6Ni_0.4O₃-800 showed the best reactivity and thermal stability,and its H₂/CO ratio maintained at the ideal value（about 1.5）.The Silicalite-1 molecular sieve was successfully prepared by hydrothermal synthesis method,and as a support mechanically mixed with the La_0.6Ce_0.4Fe_0.6Ni_0.4O₃sample.The series of x wt.%Silicalite-1/La_0.6Ce_0.4Fe_0.6Ni_0.4O₃（x=5,10,15 and 20）oxygen carrier were prepared.The Silicalite-1 improved the structural properties of La_0.6Ce_0.4Fe_0.6Ni_0.4O₃ sample.With the increase of Silicalite-1 doped content,the CO selectivity,CH₄conversion,and syngas production gradually increased.