Tubular La0.7Ca0.3Fe0.85 Co0.15O3-δPerovskite Membranes, Part II: Performance and Stability

Oxygen permeability through the tubular La0.7Ca0.3Fe0.85 Co0.15O3-δ perovskite membrane prepared by thermoplastic extrusion was measured in the temperature range from 800° to 1040°C in an air/argon gradient, and compared with the oxygen permeability of planar membranes prepared by injection molding and cold isostatic pressing. Oxygen flux through the perovskite membranes was controlled by bulk diffusion of oxygen and was not limited by surface exchange reactions. The oxygen flux through perovskite membranes normalized to 1mm wall thickness at 900°C μmol (cm2s)-1. The activation energy of oxygen diffustion was 128 kJ mol -1. The tubular membrane was tested in a reactor for partial oxidation of methane for more than 1900h. The oxygen flux decreased gradually during the test from 1.5 to 1 μmol (cm2s)-1. The methane conversion could be adjusted to 83%-88%, with the CO selectivity in the same range. After the test, a degradation of the perovskite structure of the membrane was observed. A possible mechanism for the phase degradation and segregation was proposed.