Silica based hydrogen permselective membranes for the thermochemical water splitting IS process
M. Nomura1, A. Shibata1, A. Ikeda1, O. Myagmarjav2, N. Tanaka2, S. Kubo2
1
Shibaura Institute of Technology, Dept. of Applied Chemistry, Koto-ku, Japan
2
Japan Atomic Energy Agency, HTGR Hydrogen and Heat Application Research Center, Ibaraki, Japan
The thermochemical water splitting IS process is one of the hydrogen production method by recycling I2
and SO2. One of the problems of the IS process is low conversion of the HI decomposition reaction at
about 20%. A membrane reactor to extract H2 through a H2 permselective membrane can be a solution
to improve the HI conversion. Silica hybrid membranes have been developed for silica based H2
permselective membranes by using a counter diffusion chemical vapor deposition (CVD) method. Two
reactants (e.g. silica precursor and oxidant) are provided at the opposite side of the porous substrates and
silica layer is deposited inside the pore of the substrate. The pore sizes are controlled by introducing
organic functional groups to silica precursor. In this study, the silica based membranes with the high H2
permselectivity were developed for a membrane module. Effects of pore sizes on the H2 permeances
were discussed. Porous γ-alumina substrates were employed for a CVD treatment. Hexyltrimethoxysilane
(HTMOS) was used as a silica precursor and O2 or O3 is used as an oxidant. The HI permeation
performances were investigated through the HTMOS derived membrane deposited at 450°C. Fig. 1 shows
the single gas permeation tests of H2 and HI at room temperature or 400°C. The H2 permeance was
9.4×10-7 mol m-2 s-1 Pa-1 and the H2/SF6 permeance ratio was at 420 at room temperature. The H2/HI
permeance ratio at 400°C was 6820 with the H2 permeance of 5.0×10-7 mol m-2 s-1 Pa-1. The H2
permeances kept after the HI gas permeation test at 400°C for 3 h. These results showed that the HTMOS
derived membrane can be applied as the H2 permselective membrane of the HI decomposition
reaction.**This work was supported by Council for Science, Technology and Innovation(CSTI), Crossministerial Strategic Innovation Promotion Program (SIP), “energy carrier” (Funding agency: JST).