Boreskov Institute of Catalysis of the Siberian Branch of Russian ...

OP-III-6SOME PROPERTIES OF PEROVSKITE-LIKE FERRITES AND THEIRPERFORMANCE IN MEMBRANE CATALYTIC REACTORSFOR PARTIAL OXIDATION OF NATURAL GASV.L. Kozhevnikov, I.A. Leonidov, M.V. PatrakeevInstitute of Solid State Chemistry, Ural Branch of Russian Academy of Sciences91 Pervomaiskaya Str., GSP-145, Yekaterinburg 620041, Russiafax: +7 (343) 374 4495, e-mail: kozhevnikov@ihim.uran.ruAt the present time, the technology based on use of mixed-conducting membranes isconsidered as the most promising approach for syngas production from natural gas. However,the application is still considerably hindered by absence of membrane materials, which wouldsatisfy special requirements. In addition to high mixed oxygen ion and electron conductivity,the oxygen semi-permeable ceramics should maintain thermodynamic and dimensionalstability under harsh operation conditions, mechanical strength and compatibility with othercomponents of electrochemical reactors, moderate costs, etc. In order to develop bettermaterials one may either try to enhance the ion mobility in stable materials by taking intoaccount structure-mobility relations, defect ordering, etc. or to study the thermodynamics andstability limitations in highly defective oxide materials with the pursuit of improving theirstability. The search requires experimental efforts aimed at evaluation of ion and electronconductivities, mobility and concentration of charge carriers, with emphasis on stronglyreducing conditions. Moreover, a correct evaluation of changes in oxygen stoichiometry withworking conditions is very important to confirm estimates of defect concentrations and thedefect chemistry models. In order to identify the effects of doping upon structural stabilityand transport properties a number of ferrites with perovskite related structure were appraisedemploying dilatometry, oxygen permeation studies, total conductivity and thermopowermeasurements in a wide oxygen partial pressure range at temperatures within 650-1000 °C. Itis shown that some ferrites exhibit advantageous combination of properties, and may beconsidered as viable candidate materials for oxygen separating membranes. In support ofthese findings bench scale prototype reactors with the yield of syngas up to 100 L/hdemonstrate stable parameters during several months of operation.102