Mixed-conducting dense ceramic membranes for air separation and natural gas conversion.
Non-perovskite SrFeCo{sub 0.5}O{sub x} (SFC2) was found to have high electronic and ionic conductivities as well as structural stability. At 800 C in air, total and ionic conductivities of 17 and 7 S{center_dot}cm{sup -1} were measured, respectively; the ionic transference number was calculated to be {approx}0.4. This material is unique because of its high electronic conductivity and comparable electronic and ionic transference numbers. X-ray diffraction analysis showed that air-sintered SFC2 consists of three phase components, {approx}75 wt% Sr{sub 4}(Fe{sub 1-x}Co{sub x}){sub 6}O{sub 13 {+-}{delta}}, {approx}20 wt% perovskite Sr(Fe{sub 1-x}Co{sub x}O{sub 3-{delta}}), and {approx}5 wt% rock salt CoO. Argon-annealed SFC2 contains brownmillerite Sr{sub 2}(Fe{sub 1-x}Co{sub x}){sub 2}O{sub 5} and rock salt CoO. Dense SFC2 membranes were able to withstand large pO{sub 2} gradients and retain mechanical strength. A 2.9-mm-thick disk membrane was tested in a gas-tight electrochemical cell at 900 C; an oxygen permeation flux rate {approx}2.5 cm{sup 3}(STP){center_dot}cm{sup -2}{center_dot}min{sup -1} was measured. A dense thin-wall tubular membrane of 0.75-mm thickness was tested in a methane conversion reactor for over 1,000 h. At 950 C, the oxygen permeation flux rate was {approx}10 cm{sup 3}(STP){center_dot}cm{sup -2}{center_dot}min{sup -1} when the SFC2 thin-wall membrane was exposed with one side to air and the other side to 80% methane balanced with inert gas. Results from these two independent experiments agreed well. The SFC2 material is a good candidate as dense ceramic membranes for oxygen separation from air or for use in methane conversion reactors.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- FETC
- DOE Contract Number:
- DE-AC02-06CH11357
- OSTI ID:
- 914768
- Report Number(s):
- ANL/ET/CP-111297; TRN: US200812%%267
- Journal Information:
- J. Solid State Electrochem., Vol. 10, Issue 8 ; Aug. 2006; Conference: 225th ACS National Meeting; Mar 23-27, 2003; New Orleans, LA
- Country of Publication:
- United States
- Language:
- ENGLISH
Similar Records
Structure and property relationship in the mixed-conducting Sr-Fe-Co-O system.
Oxygen-permeable ceramic membranes for gas separation