Mesoporous CeO₂-ZrO₂-γ-Al₂O₃ nanocomposite membranes exhibiting remarkable hydrothermal stability

Abstract

The CeO₂-ZrO₂-γ-Al₂O₃ nanocomposite was synthesized through the sol-gel route by mixing a boehmite sol (AlOOH) with an appropriate amount of metal nitrates. By using this multicomponent sol, crack and pinhole free mesoporous membranes were successfully fabricated on an asymmetric porous α-Al₂O₃ support through dip coating process. The hydrothermal (up to 75% steam) stability of the mesoporous membranes was studied in terms of hydrogen gas permeance at 500EC, phase structure, surface microstructure and pore size distribution. The pore size distribution measurements were conducted directly on the membranes by a nano-permporometer. Among the tested samples with different molar compositions of CeO₂-ZrO₂-γ-Al₂O₃, only the mesoporous CeO₂-ZrO₂-γ-Al₂O₃ membrane with a molar ratio of 10:10:80 mol% was found to be the most effective membrane under the hydrothermal condition at 500EC. The ternary CeO₂-ZrO₂-γ-Al₂O₃ system retained its structure (order and porosity) after crystallization on an α-Al₂O₃ porous support and subsequent hydrothermal treatment for over 50 h. The hydrothermal test indicates that the mesoporous membrane developed in this study is viable to be used as an intermediate layer for fabricating a multilayer hydrogen separation membrane reactor for the methane steam reforming reaction.

Keywords:

• Mesoporous membrane
• Ce-Zr solid solution
• γ-Al₂O₃
• Gas permeance
• Hydrothermal stability