Synthesis of dense oxygen-selective perovskite membranes on porous stainless steel tubes

摘要

Ar elevated temperatures (>973 K), solid-solution compositions in the (La, Sr) (Co, Fe)O_(3 - δ), system (ABO_3 perovskite structure) exhibit substantial ionic and electronic conductivity, making them attractive as membrane materials for air separation or as combined oxygen supplying membrane and catalyst in membrane reactors [1-10]. Provided that the mixed-conducting membrane is fully dense, it is only permeation selective to oxygen. Previous studies on these membranes have focused on developing new materials and components, and thus 1-3 mm thick disk-shaped [1-7] or tubular [8-10] symmetric membranes have been used. However, the potential problem, which may prevent their industrial applications, is their relative low oxygen permeation fluxes. A solution to this is fabrication of thin dense film ( < 0.1 mm) on porous support to reduce the oxygen transport resistance. In 1989, Teraoka et al. [11] prepared La_(0.6)Sr_(0.4)CoO_(3 - δ) membranes on porous La_(0.6)Sr_(0.4)CoO_(3 - δ) supports by sputtering, but their membranes were not completely gas-tight. Recently, sol-gel processing [12], CVD [13] and pulsed laser deposition [14] have been used, and the prepared membranes were reported to be defect-free. However, the calcination or deposition temperatures of these techniques were 973 K or less, which are lower than the typical operation temperature ( > 973 K) if the membranes are employed in oxygen separators or membrane reactors.