Identification of Molecular Transport Mechanisms in Micro-Porous Hydrotalcite–Silica Membrane

• Published in: Transport in porous media Vol. 104; no. 1; pp. 133 - 144
• Main Authors: Wiheeb, A. D., Ahmad, M. A., Murat, M. N., Kim, J., Othman, M. R.
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01.08.2014; Springer; Springer Nature B.V
• Subjects: Affinity; Aluminum oxide; Binary mixtures; Carbon dioxide; Civil Engineering; Classical and Continuum Physics; Earth and Environmental Science; Earth Sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Exact sciences and technology; Gas flow; Geotechnical Engineering & Applied Earth Sciences; Heat treatment; High temperature; Hydrocarbons; Hydrogeology; Hydrology. Hydrogeology; Hydrology/Water Resources; Industrial Chemistry/Chemical Engineering; Membranes; Permeability; Pollution, environment geology; Porosity; Sedimentary rocks; Silicon dioxide; Simulation; Substrates; Surface chemistry; Transitional aluminas; Transport; Viscous flow; Hydrotalcite; Gas separation; Permeability; Porous membrane; Greenhouse gases; experimental studies; carbon dioxide; adsorption; diffusion; nitrogen; porosity; silica; permeability; flow mechanism; digital simulation; hydrogen; pressure; transport; high temperature; alumina; separation; substrates; porous media; gases
• ISSN: 0169-3913; 1573-1634
• DOI: 10.1007/s11242-014-0324-5

Hydrotalcite (HT) materials have been known to be able to adsorb CO 2 even at high temperature. However, HT has not been made into a micro-porous membrane because of its meso-porous nature. In order to form a micro-porous HT membrane, silica was selected as a host matrix due to its ability to retain its micro-porosity. In this paper, a micro-porous hydrotalcite–silica membrane was formed on a meso-porous γ -alumina layer supported by a macro-porous α -alumina substrate. Most of the micro-porosity determined from nitrogen adsorption measurement was found to be either closed or open but not interconnected, whereas most of the meso-porosity (at ca. 11.2 nm) in the micro-porous membrane was open and interconnected, thereby promoting gas flow. Viscous flow mechanism was observed to dominate transport of gases in macro-porous membrane. Knudsen diffusion dominated transport of gases in meso-porous membrane. On the other hand, surface affinity influenced the transport of carbon dioxide through the micro-porous membrane rather significantly. While permeability of pure hydrogen and carbon dioxide were independent of pressure, the permeability of the gases in the binary mixtures decreased with increasing pressure. Both experiment and simulation demonstrated consistent results.