Construction of new electrochemical-membrane-reactor system for simulutaneous environmental purification/chemical conversation

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In this research project, we investigated each process of the newly proposed electrochemical membrane-reactor system and obtained the following results.(1)Oxygen permeation property of the barium ferrites(Ba-Fe system) was examined. Partial substitution of Ba by rare earth metals as well as alkaline earth metals was found to stabilize cubic perovskite structure even at room temperature. It was also found that oxygen permeation appeared at lower temperature. Partial substitution of Fe by Ni,Mg,or Zn was quite effective for improvement of oxygen permeability. (2)Fe/Mn-based perovskites exhibited oxygen permeability and high stability against the reduction, and could be used as quite stable oxygen permeable membranes in the membrane reactors catalyzing the partial oxidation of methane and the reduction of NO by methane. In addition, Ba/Sr/Fe-based perovskites was found to be one of most excellent oxygen permeable materials. (3)Perovskite oxide of LaGaO_3 doped with Sr and Fe(LSGF) was found to exhibit high electrical conductivity, oxygen permeation rate and chemical stability, and this LSGF could be used for oxygen permeation membrane for CH_4 partial oxidation. Hole conduction is dominant in LSGF in wide Po_2 range and temperature. In addition, oxygen permeation rate in various oxides was investigated and Pr_2NiO_4 doped with Gu was found to give high oxygen permeation rate from air to He. (4)Preparation of porous disk was attempted to fabricate thin films on it for the purpose of improving oxygen permeability of mixed conductive perovskite-type oxides. Oxalate precursor method was found to give porous disks with a narrow distribution of pore diameter even at elevated temperature. The disks obtained by the oxalate precursor method showed high nitrogen-permeability feasible for practical applications.