Properties of Hydrogen-Selective TiO_2 composite Membranes Prepared by CVD of Metal Alkoxide

摘要

Thin films of TiO_2 and TiO_2/SiO_2 were deposited on the inner surface of the porous glass support tubes by the decomposition of tetraisopropyl titanate (TIPT) and tctraethyl orthosilicate (TEOS) at atmospheric pressure. Deposition rate of the films and permeation properties of the membranes prepared were much different depending on the deposition conditions such as temperature and TIPT/TEOS ratio in the feed stream. The pure TiO_2 films which were deposited only in the temperature range between 230 and 300℃ appeared to have some hydrogen selectivity. In comparison to the pure TiO_2 films, composite TiO_2/SiO_2 films could be formed at temperatures as high as 600℃ and they showed excellent hydrogen permeability which is comparable to that of the pure silica films. And the deposition rates of TiO_2/SiO_2 films were much faster than those of the pure SiO_2 films. The permeation rates of H_2 through the TiO_2/SiO_2 membrane at 600℃ were 0.2-0.4 cm~3/min-cm~2 -atm and H_2:N_2 permeation ratio were above 1000.