Abstract: Hydrophobic organic-inorganic hybrid silica sols were prepared using 1,2-bis(triethoxysilyl)ethane(BTESE) and 1H,1H,2H,2H-perfluorodecyltriethoxysilane(PFDTES) as precursors under acidic condition, then the sols were deposited on γ-Al₂O₃/α-Al₂O₃ substrates by dip-coating under clean room condition. The cross-sectional morphology, particle size of the sols and hydrophobic property of the membranes were characterized by means of SEM, DLS, FTIR, water contact angle measurement and thermogravimetric analysis. The results show that the particle size of sols and the water contact angle of supported membranes increase with increasing the amount of PFDTES in the mixture. A narrow sol particle size distribution centered at 3.69 nm and a water contact angle of (112.0±0.4)º were obtained at a BTESE/PFDTES molar ratio of 0.25: 1. At 300℃, the membrane shows a high H₂ permeance of 5.99×10^-7 mol·m^-2·Pa^-1·s^-1 and a H₂/CO and H₂/CO₂ permselectivity of 9.54 and 5.20, respectively, which were higher than the corresponding Knudsen value(H₂/CO=3.74, H₂/CO₂=4.69). The H₂ transport in the modified silica membranes is subjected to a micropore diffusion mechanism.

Key words: Organic-inorganic hybrid silica membrane, Sol-gel technique, Hydrophobic property, Gas separation