Synthesis of Perovskite-Type La_0.7Sr_0.3Co_0.5Fe_0.5O_3-δ Oxide Membranes and Their Oxygen Permeation Performance in Different Atmospheres for Carbon Dioxide-Oxygen Separation

Abstract

In the present study, La_0.7Sr_0.3Co_0.5Fe_0.5O_3-δ powders have been prepared by thermal decomposition of amorphous citrate precursors by calcination at high temperature. The material properties are characterized by thermogravimetric-differential thermal analysis, X-ray diffraction, and four probe method. A perovskite structure with rhombohedral symmetry has been certified for the selected La_0.7Sr_0.3Co_0.5Fe_0.5O_3-δ oxide membranes. The electrical conductivity of sintered La_0.7Sr_0.3Co_0.5Fe_0.5O_3-δ ceramics increases with temperature through a maximum, then decreases at relatively higher temperatures, due to oxygen vacancy formation. Oxygen permeation was performed between 700 and 950°C under different oxygen partial pressures (0.21, 0.42, and 0.63 atm) and carbon dioxide concentrations (300, 500, and 700 ppm). According to Arrhenius' law, the oxygen permeation flux of the membranes with a thickness of 1.1 mm increases with temperature and oxygen partial pressure. A maximum oxygen flux of ~0.33 mL/min · cm² and ~0.25 mL/cm² · min was measured at 950°C at high oxygen pressure (P_O2 = 0.63 atm) and under carbon dioxide concentration range from 300 to 700 ppm, respectively.