Description: The most significant cost associated with the conventional partial oxidation of methane is that of an oxygen plant. Our new technology offers a way to lower this cost, and in this paper we explore the technology that is based on dense ceramic membranes and that uses air as the oxidant for methane-conversion reactions. Mixed-conducting ceramic materials have been produced from mixed-oxide systems of the La-Sr-Fe-Co-O (SFC) type, in the form of tubes and bars. Thermodynamic stability of the tubes was studied as a function of oxygen partial pressure by high-temperature XRD. Mechanical properties were measured and found to be adequate for a reactor in the case of SFC-2: Electronic and ionic conductivities were measured; SFC-2 is unique in the sense that the 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 the consequence of an oxygen gradient that introduced a volumetric lattice difference between the inner and outer walls. SFC-2 tubes provided methane conversion efficiencies of >99% in a reactor. These tubes have operated for >1000 h.
Date: May 1, 1995
Creator: Balachandran, U.; Dusek, J.T.; Maiya, P.S.; Mieville, R.L.; Kleefisch, M.S.; Udovich, C.A. et al.
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