Evaluating the chemical stability of metal oxides in SO3 and applications of SiO2-based membranes to O2/SO3 separation |
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Authors: | Xin Yu Lie Meng Hiroki Nagasawa Masakoto Kanezashi Masato Machida Toshinori Tsuru |
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Affiliation: | 1. Department of Chemical Engineering, Graduate School of Engineering, Hiroshima University, Higashi-Hiroshima, Japan;2. Division of Materials Science and Chemistry, Faculty of Advanced Science and Technology, Kumamoto University, Kumamoto, Japan |
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Abstract: | The decomposition of sulfur trioxide to produce sulfur dioxide and oxygen using a catalytic membrane reactor is technology that promises to improve the economic viability of the thermochemical water-splitting Iodine-Sulfur (IS) process for large-scale CO2-free hydrogen production. The chemical stability of membrane materials under SO3, however, is a significant challenge for this strategy. In this study, microporous membranes with a layered structure that consisted of a membrane support prepared from α-Al2O3, an intermediate layer prepared from silica-zirconia, and a top layer prepared from bis (triethoxysilyl)ethane-derived organosilica sols, were examined for stability under SO3 and for use in SO3/O2 separation. An α-Al2O3 support that features SiO2–ZrO2 intermediate layers with large pore sizes and a high Si/Zr molar ratio showed excellent resistance to SO3, which was confirmed by N2 adsorption, Energy Dispersive X-ray Spectroscopy (EDS), and Scanning Electron Microscopy (SEM). These membranes also demonstrated a negligible change in gas permeance before and after SO3 exposure. Subsequently, in binary-component gas separation at 550°C, microporous organosilica-derived membranes achieved an O2/SO3 selectivity of 10 (much higher than the Knudsen selectivity of 1.6) while maintaining a high O2 permeance of 2.5 × 10−8 mol m–2 s–1 Pa–1. |
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Keywords: | membranes porous materials silica sol-gel zirconia |
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