HYDROGEN PRODUCTION FROM METHANE BY USING OXYGEN PERMEABLE CERAMICS

摘要

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 methane reforming property of a novel member of oxygen permeable ceramics. The materials used are solid solutions of (La_(0.5)Ba_(0.3)Sr_(0.2))(Fe_xIn_(1-x))O_(3-δ). The single phase of perovskite-type (La_(0.5)Ba_(0.3)Sr_(0.2))(Fe_xIn_(1-x))O_(3-δ) is obtained in the range of x = 0.4 to 0.9. The highest oxygen flux densities of 2.2 and 11 μmoL/cm~2 s are attained for (La_(0.5)Ba_(0.3)Sr_(0.2))(Fe_xIn_(1-x))O_(3-δ) (x = 0.6) at 1000 ℃ under He / air and CH_4 / air gradients, respectively. The electrical conductivity of (La_(0.5)Ba_(0.3)Sr_(0.2))(Fe_xIn_(1-x))O_(3-δ) is dominated by p-type conduction having a slope of 1/4 under the high P(O_2) region. The oxide-ion conductivity of the same sample is estimated to be 0.05 S/cm at 800℃. Even though the oxygen flux density slightly decreases with increasing time, high CO selectivity of 90 % is kept for 100 h. The oxygen flux density of the solid solution is also discussed in the context of surface exchange kinetics.