SrAl2O4-improved SrCo0.8Fe0.2O3−δ mixed-conducting membrane for effective production of hydrogen from methane

A series of SrAl2O4 (3, 5, 7 and 9 wt.%, respectively) doped SrCo0.8Fe0.2O3−δ (SCF) mixed-conducting materials were prepared by a gel-combustion method and then a solid state reaction process. The crystal structure, thermal expansion behavior, microstructure, electrical conductivity, oxygen permeability and structure stability of these materials were systematic investigated. The prepared SrAl2O4-doped SCF oxides presented single-phase perovskite structure and no obvious impurity phases can be observed. The thermal expansion coefficients, electrical conductivity and oxygen permeability of these materials decreased with increasing the doping amount of SrAl2O4. 5-7 wt.% SrAl2O4 was proper to stabilize the perovskite structure of SCF at high temperature and under low oxygen partial pressures. 5 wt.% SrAl2O4-doped SCF (SCFSA5) membrane reactor was constructed for hydrogen production from methane. This membrane reactor exhibited high performance and good stability for hydrogen production. At 850 °C, the CH4 conversion, hydrogen selectivity, hydrogen production and oxygen permeation flux remained at about 75%, 91%, 25 ml(STP) cm−2 min−1 and 8 ml(STP) cm−2 min−1, respectively, for more than 1200 h.