abstract
Thermodynamic calculations with additional conditions for the conservation of carbon and hydrogen were used to predict the gas composition obtained by partial oxidation of methane as a function of oxygen partial pressure and temperature; this was used to assess the stability and oxygen permeability requirements of mixed conducting membrane materials proposed for this purpose. A re-examination of known mixed conductors shows that most materials with highest permeability still fail to fulfil the requirements of stability under reducing conditions. Other materials possess sufficient stability but their oxygen permeability is insufficient. Different approaches were thus used to attempt to overcome those limitations, including changes in composition in the A and B site positions of ABO(3) perovskites, and tests of materials with different structure types. Promising results were obtained mainly for some materials with perovskite or related K2NiF4-type structures. Limited stability of the most promising materials shows that one should rely mainly on kinetic limitations in the permeate side to protect the mixed conductor from severe reducing conditions.
keywords
ELECTROCHEMICAL PERMEABILITY; OXYGEN PERMEABILITY; CERAMIC MEMBRANES; STABILITY; TRANSPORT; PERMEATION; EXCHANGE; OXIDES; CO; CR
subject category
Materials Science
authors
Frade, JR; Kharton, VV; Yaremchenko, AA; Tsipis, EV; Shaula, AL; Naumovich, EN; Kovalevsky, AV; Marques, FMB
our authors
Aleksey Yaremchenko
Principal Researcher
Andrei Kavaleuski
Principal Researcher
Fernando Manuel Bico Marques
Full professor
Jorge Ribeiro Frade
Retired Professor