Fabrication and characterization of dense ceramic membranes for partial oxidation of methane

摘要

In this technology, air is used as the oxidant for methane conversion reactions, thiu eliminating tne need for an expensive oxygen plant. Mixed-conducting ceramic materials have been produced from mixed-oxide system of the La-Sr-Fe-Co-O (SFC) type, in the form of tubes and bars. Thermodynamic stability of the tubes was studied vs oxygen partial pressure by high-temperature XRD. Mechanical properties of the SFC-2 (SrFeCo(sub 0.5)O(sub x)) material were adequate for reactor use. Electronic and ionic conductivities showed that SFC-2 is unique in that its ratio of ionic to electronic conductance is close to unity. Performance of the membrane tubes was good only with SFC-2. Fracture of other SFC tubes was consequence of an oxygen gradient that introduced a volumetric lattice difference between the inner and outer walls. SFC-2 tubes provided methane conversion efficiencies >99% in a reactor and have operated successfully for >1000 h.