Preparation And Hydrogen Separation Property Of Organic-Inorganic Hybrid Silica Membranes Modified By Perfluorodecyl Group

Microporous silica membranes are considered to be one of the most promisingmaterials for hydrogen separation due to their thermal and chemical stability, highmechanical strength, porosity, and tailorability. However, silica membranes lacklong-term hydrothermally stability if exposed to water, which may lead to silicamembranes’ amorphous networks hydrolysis at temperature as low as60°C, resultingin a defective structure with large pores and the loss of gasselectivity.It is convincedthat silanols（hydroxyl） groups on the pore surface are inclined to absorb watermolecules; consequently, replacing the silanols by the incorporation of hydrophobicstable organic groups is an effective method to achieve the hydrothermal stability ofsilica membranes.In this paper, the organic-inorganic hybrid silica membranes modified byperfluorodecyl groups was prepared by the sol-gel technique using1,2-Bis（triethoxysilyl）ethane and1H,1H,2H,2H-Perflouorodecyltriethoxysilane asprecursors under acidic condition and deposited on γ-Al₂O₃/-Al₂O₃porous ceramicsubstrates by dip-coating under clean room condition, then calcined in a nitrogen flow.The particle size of sol, the hydrophobic property, and the cross-sectional morphologyof organic-inorganic hybrid silica membranes were characterized by means of DLS,water contact angle measurement, FT-IR, thermogravimetric analysis, and SEM. Gaspermeation and separation performance of the supported organic-inorganic hybridsilica membranes was performed on a home-made setup.The results show that the particle size of sol and the water contact angle ofsupported membranes increases with the amount of PFDTES in the mixture. A narrowsol particle size distribution centers on3.69nm and a water contact angle of112.0±0.4°is obtained at a PFDTES/TEOS molar ratio of0.25.The FT-IR spectra and the TGanalysis results demonstrate the excellent hydrophobic property of（0.25PFDTES）BTESE, and meanwhile the SEM images indicate that a silica toplayerhas been successfully deposited on the γ-Al₂O₃/-Al₂O₃substrates..The results of gas permeation and separation suggest that the transportation ofhydrogen in the hybrid silica membranes abides by the microporous diffusionmechanism.At300°C, the organic-inorganic hybrid silica membranes show a highhydrogen permeance of9.67×10^-7mol·m^-2·Pa^-1·s^-1and a H₂/CO and H₂/CO₂ permselectivity of13.07and5.67respectively, higher than their correspondingKnudsen value （H₂/CO=3.74, H₂/CO₂=4.69）.