Hydrogen Production From Methane by Using Oxygen Permeable Ceramics

Oxygen permeable ceramics based on mixed conductors are attracting much attention for use in partial oxidation of hydrocarbons as a novel technique for syngas and pure hydrogen production. This paper describes the preparation and oxygen permeation properties including the methane reforming property of a novel member of oxygen permeable ceramics. The materials used are solid solutions of $(La0.5Ba0.3Sr0.2)(FexIn1−x)O3−δ$⁠. The single phase of perovskite-type $(La0.5Ba0.3Sr0.2)(FexIn1−x)O3−δ$ is obtained in the range of $x=0.4$ to 0.9. The highest oxygen flux densities of 2.2 and $11μmol∕cm2s$ (membrane thickness, $L=0.2mm$⁠) are attained for $(La0.5Ba0.3Sr0.2)(FexIn1−x)O3−δ$$(x=0.6)$ at $1000°C$ under He/air and $CH4$/air gradients, respectively. The electrical conductivity of $(La0.5Ba0.3Sr0.2)(Fe0.6In0.4)O3−δ$ is dominated by $p$-type conduction having a slope of $1∕4$ under the high $P(O2)$ region. The oxide-ion conductivity of the same sample is estimated to be $0.05S∕cm$ at $800°C$⁠. Even though the oxygen flux density slightly decreases with increasing time, high CO selectivity of 90% is kept for $100h$⁠. The oxygen flux density of the solid solution is also discussed in the context of surface exchange kinetics.