(142c) Hybrid Membranes for Improved Molecular Separation in Gas and Liquid-Phase

Hybrid membranes have been investigated for improved performance which cannot be achieved by using only one type of materials. In this talk, our recent progresses on hybrid membranes will be introduced, including organosilica where Si was hybrid with organic functional groups on the molecular level, and mixed-matrix-membranes where inorganic nanoparticles were hybrid with polyamide during interfacial polymerization.

Amorphous silica membranes show highly permselectivity for hydrogen; however, there still remain two technical challenges: pore size control and hydrothermal stability.¹⁾ In order to improve hydrothermal stability of silica membranes, Castricum et al.²⁾ developed hybrid silica membranes using bis (triethoxysilyl)ethane (BTESE), which showed excellent hydrothermal stability in pervaporation of aqueous alcohol solutions because of incorporated organic linking groups (Si-C-C-Si unit) in silica networks. We recently proposed a new strategy to control pore sizes of silica membranes using bridged alkoxides.^3-8) Bis (tri-ethoxysilyl) ethane (BTESE), consisting of ethane group between 2 silicon atoms (-Si-CH₂-CH₂-Si-) as the minimum unit in hydrolysis and condensation reaction, was found to lead to loose silica networks. BTESE silica membranes showed approximately one order magnitude high H₂ permeance (~10^-5 mol/(m² s Pa)) compared with previously reported silica membranes using TEOS (tetraethoxysilane), and a high H₂ to SF₆ permeance ratio of more than 1,000 with a low H₂ to N₂ selectivity (~10).³⁾ Applications, including gas separation (hydrogen, organic gas^3-6)) and liquid phase separation (reverse osmosis⁷⁾, pervaporation⁸⁾), will be also discussed. BTESE membrane showed quite high rejection for NaCl and high stability to chlorine in reverse osmosis.

Regarding polyamide (PA) membranes for reverse osmosis, we proposed spray-assisted, 2-step interfacial polymerization⁹⁾. We found the formation of multilayered ridge-and-valley structures via the first spray-assisted interfacial polymerization, leading enhanced water permeation due to increased surface area. Zeolite Y nanoparticles, which were embedded into PA layer in the first-spray process, were confirmed to increase water permeability.

References  

1) T. Tsuru, J. Sol-Gel Sci. Technol., 46 (2008) 349;  J. Japan Petroleum Institute 54 (2011) 277.  2) H.L. Castricum, A. Sah, R. Kreiter, D.H.A. Blank, J.F. Vente, J.E. ten Elshof,, J. Mater. Chem. 18 (2008) 2150.  3) M. Kanezashi, K. Yada, T. Yoshioka, T. Tsuru, J. Am. Chem. Soc. 131 (2009) 414.  4) H. R. Lee, M. Kanezashi, T. Yoshioka, T. Tsuru, AIChE J. 57 (2011) 2755.  5) G. Li, M. Kanezashi, T. Tsuru, J. Membr. Sci. 379 (2011) 287.  6) M. Kanezashi, M. Kawano, T. Yoshioka, T. Tsuru, Ind. Eng. Chem. Res. 51 (2012) 944.  7) R. Xu, J. Wang, M. Kanezashi, T. Yoshioka, T. Tsuru, Langmuir 27 (2011) 13996.  8) T. Tsuru, T. Shibata, M. Kanezashi, T. Yoshioka, J. Membr. Sci. 421-422 (2012) 25-31  9) T. Tsuru, S. Sasaki, T. Kamada, T. Shintani, T. Ohara, H. Nagasawa, K. Nishida, M. Kanezashi, T. Yoshioka, J. Membr. Sci. submitted.