Fe/Mn-based Perovskite-Type Oxides with Excellent Oxygen Permeability and Reduction Tolerance

摘要

A family of Co-free, Fe/Mn-based perovskite-type oxides, (Sr, A')(Fe, Mn)O_(3-δ) (A'=La, Ba, Ca), was synthesized, and their oxygen permeability and phase stability in reducing atmosphere were investigated. The substitution of Mn at B site caused the decrease in oxygen permeability. As for the effect of A-site substitution, prominent promotion was observed by the substitution of Ba for 30% of Sr, and Ba_(0.3)Sr_(0.7)FeO_(3-δ) was found to be one of most excellent oxygen permeable materials with the permeation flux of 3.0 cm~3(STP) cm~(-2) min~(-1) at 900℃. Reduction tolerance was evaluated by TG measurements in a 5%H_2/N_2 stream up to 1000℃. After the TG measurements, crystal structures of La-Sr-Co-Fe-O and Sr-Fe-(Mn)-O perovskites were decomposed or transformed into low oxygen permeable phases, but the perovskite-type structure of Ba-Sr-Fe-(Mn)-O survived. The Fe/Mn-based perovskites with high oxygen permeability and exceeding reduction tolerance could be used as stable membrane materials for membrane reactors catalyzing NO-CH_4 reaction and the partial oxidation of CH_4 into synthesis gas.