SrAl 2O 4-improved SrCo 0.8Fe 0.2O 3− δ mixed-conducting membrane for effective production of hydrogen from methane

Abstract

A series of SrAl 2O 4 (3, 5, 7 and 9 wt.%, respectively) doped SrCo 0.8Fe 0.2O 3− 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 SrAl 2O 4-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 SrAl 2O 4. 5–7 wt.% SrAl 2O 4 was proper to stabilize the perovskite structure of SCF at high temperature and under low oxygen partial pressures. 5 wt.% SrAl 2O 4-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 CH 4 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.