title: Enhanced oxygen separation through robust freeze-cast bilayered dual-phase membranes.
abstract: Dual-phase oxygen-permeable asymmetric membranes with enhanced oxygen permeation were prepared by combining freeze-casting, screen-printing, and constraint-sintering techniques. The membranes were evaluated under oxyfuel operating conditions. The prepared membranes are composed of an original ice-templated La(0.6)Sr(0.4)Co(0.2)Fe(0.8)O(3-δ) support with hierarchically oriented porosity and a top fully densified bilayered coating comprising a 10 μm-thick La(0.6)Sr(0.4)Co(0.2)Fe(0.8)O(3-δ) layer and a top protective 8 μm-thick layer made of an optimized NiFe2O4/Ce(0.8)Tb(0.2)O(2-δ) composite synthesized by the one-pot Pechini method. Preliminary analysis confirmed the thermochemical compatibility of the three involved phases at high temperature without any additional phase detected. This membrane exhibited a promising oxygen permeation value of 4.8 mL min(-1)  cm(-2) at 1000 °C upon using Ar and air as the sweep and feed gases, respectively. Mimicking oxyfuel operating conditions by switching argon to pure CO2 as a sweep gas at 1000 °C and air as feed enabled an oxygen flux value of 5.6 mL min(-1)  cm(-2) to be reached. Finally, under the same conditions and increasing the oxygen partial pressure to 0.1 MPa in the feed, the oxygen permeation reached 12 mL min(-1)  cm(-2). The influence of CO2 content in the sweep gas was studied and its reversible and positive effect over oxygen permeation at temperatures equal to or above 950 °C was revealed. Finally, the membrane stability over a period of 150 h under CO2-rich sweep gas showed a low degradation rate of 2.4×10(-2)  mL min(-1)  cm(-2) per day.
authors: Instituto de Tecnología Química, Universidad Politécnica de Valencia-Consejo Superior de Investigaciones Científicas, Avenida de los Naranjos, s/n, 46022 Valencia (Spain), Fax: (+34) 963877809.
authors: Cyril
authors: C
authors: Gaudillere
authors: Julio
authors: J
authors: Garcia-Fayos
authors: María
authors: M
authors: Balaguer
authors: José M
authors: JM
authors: Serra
mesh_terms: D005615:Freezing; D008567:Membranes, Artificial; D010100:Oxygen / Q000302:isolation & purification*; D010539:Permeability
chemical_list: D008567:Membranes, Artificial; D010100:Oxygen
keywords: dual-phase materials; freeze casting; hierarchical porosity; membranes; oxygen