High-Performance Microchanneled Asymmetric Gd_0.1Ce_0.9O_1.95−δ–La_0.6Sr_0.4FeO_3−δ-Based Membranes for Oxygen Separation

Abstract

A microchanneled asymmetric dual phase composite membrane of 70 vol % Gd(0.1)Ce(0.9)O(1.95-δ)-30 vol % La(0.6)Sr(0.4)FeO(3-δ) (CGO-LSF) was fabricated by a "one step" phase-inversion tape casting. The sample consists of a thin dense membrane (100 μm) and a porous substrate including "finger-like" microchannels. The oxygen permeation flux through the membrane with and without catalytic surface layers was investigated under a variety of oxygen partial pressure gradients. At 900 °C, the oxygen permeation flux of the bare membrane was 1.6 (STP) ml cm(-2) min(-1) for the air/He-case and 10.10 (STP) ml cm(-2) min(-1) for the air/CO-case. Oxygen flux measurements as well as electrical conductivity relaxation show that the oxygen flux through the bare membrane without catalyst is limited by the oxygen surface exchange. The surface exchange can be enhanced by introduction of catalyst on the membrane surface. An increase of the oxygen flux of ∼1.49 (STP) mL cm(-2) min(-1) at 900 °C was observed when catalyst is added for the air/He-case. Mass transfer polarization through the finger-like support was confirmed to be negligible, which benefits the overall performance. A stable flux of 7.00 (STP) ml cm(-2) min(-1) was observed between air/CO/CO2 over 200 h at 850 °C. Partial surface decomposition was observed on the permeate side exposed to CO, in line with predictions from thermodynamic calculations. In a mixture of CO, CO2, H2, and H2O at similar oxygen activity the material will according to the calculation not decompose. The microchanneled asymmetric CGO-LSF membranes show high oxygen permeability and chemical stability under a range of technologically relevant oxygen potential gradients.

Oxygen transport properties of tubular Ce0.9Gd0.1O1.95-La0.6Sr0.4FeO3−d composite asymmetric oxygen permeation membranes supported on magnesium oxide

“…It is expected that SrCO 3 formed on the surface of LSF will have no catalytic activity and will impede the surface exchange reaction. Evidence of formation of carbonates on the surface of the CGO-LSF composite membrane was reported by Cheng et al [21]. Formation and decomposition of SrCO 3 is temperature dependent.…”

“…Additionally, the small difference between the estimated effective ionic conductivities of the composite with only CGO and with CGO-LSF shows that the ionic conductivity of the membrane is dominated by the contribution from the CGO, especially at lower temperatures. where the reported D chem was within 1.6 -2.2 x 10 -4 cm 2 /s with an activation energy of 100 kJ/mol [21]. Figure 4a shows the a(O 2 ) dependence of D chem in the temperature range 750 °C to 950 °C.…”

Ceramic Membranes: Materials – Components – Potential Applications

“…This means that the modelling results can be factored into the choice of exisiting production technologies and can help to substantiate the need for new production technologies. For example, freeze casting , and phase‐inversion tape casting are currently being investigated and used for the production of particularly straight channel structures and defined pore opening diameters. These two methods are suitable for producing both planar and tubular modules, including capillaries.…”

Keramische Membranen: Materialien – Bauteile – potenzielle Anwendungen

“…So werden z. B. für die Herstellung besonders gerader Kanalstrukturen und definierter Porenöffnungsdurchmesser seit Neuestem Gefriergießen , oder das phaseninverse Foliengießen untersucht und eingesetzt . Beide Verfahren eignen sich dazu, sowohl planare als auch tubulare Träger bzw.…”