Hydrogen Production From Methane by Using Oxygen Permeable Ceramics

Abstract

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.