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Hydrogen separation in La₅.₅WO₁₁.₂₅₋δ membranes

Escolástico, Sonia, Solís, Cecilia, Scherb, Tobias, Schumacher, Gerhard, Serra, Jose M.
Journal of membrane science 2013 v.444 pp. 276-284
Raman spectroscopy, X-ray diffraction, artificial membranes, carbon dioxide, hydrogen, permeability, scanning electron microscopy, temperature
Tungstates Ln₆WO₁₂ are proton conducting crystalline materials which show significant mixed protonic and electronic conductivity and stability in moist CO₂ environments. These materials are promising candidates for hydrogen separation membranes at temperatures above 700°C, especially when integrated in intensified processes as catalytic membrane reactors. From this family of compounds, La₆₋ₓWOy (0.4<x<0.7) presents the highest protonic conductivity and hydrogen permeability. This contribution presents the preparation, hydrogen permeation and stability study of La₅.₅WO₁₁.₂₅₋δ membranes. Hydrogen separation properties of La₅.₅WO₁₁.₂₅₋δ were systematically analyzed, i.e. the influence of the H₂ concentration in feed stream, humidification degree and operating temperature were investigated. The integrity of the La₅.₅WO₁₁.₂₅₋δ after the hydrogen permeation experiments was confirmed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Raman spectroscopy. The stability of La₅.₅WO₁₁.₂₅₋δ permeation when CO₂ containing atmosphere was used as sweep gas was evaluated. Furthermore, the stability of this compound in CO₂-rich and sulfur-containing environments was confirmed by XRD.