微孔SiO2膜在水蒸气条件下的稳定性能

Hydrothermal Stability of Microporous SiO_2 Membranes

以正硅酸乙酯为前驱体,通过聚合溶胶路线制备出稳定的SiO2溶胶和制膜液,采用浸浆法,经过一次涂膜,在平均孔径约为3nm的γ-Al2O3中孔膜上制备出完整无缺陷的SiO2微孔膜,考察了烧成温度对SiO2粉末和SiO2微孔膜气体渗透性能的影响.结果表明,在400～800℃焙烧温度下制备的SiO2膜在200℃及0.3MPa条件下对He的渗透通量为(7.29～12.7)×10-7mol/(m2·s·Pa),600℃下烧成的膜的理想分离因子分别为98(He/CO2),49(He/O2),64(He/N2),79(He/CH4)和91(He/SF6),具有分子筛分效应.微孔SiO2膜在水蒸气条件下的稳定性能取决于膜的烧成温度,400,600和800℃烧成的膜的水蒸气稳定压力分别为8,200和200kPa.

Preparation and hydrotherrnal stability of microporous silica membrane were studied. A stable SiO2 polymeric sol was successfully synthesized with tetraethylorthosilicate as precursor through polymeric sol-gel route, α-Al2O3 supported defect-free mesoporous γ-Al2O3 disk membrane with average pore size of about 3 nm was fabricated via dip coating and subsequently calcined at 600℃. The effect of calcination temperature on the properties of SiO2 powder and gas permeabilities of supported SiO2 membranes, especially with regard to the hydrothermal stability of SiO2 microporous membranes, was studied in detail. The results show that He permeability of SiO2 membranes calcined at 400-800℃ was （7.29-12.7）×10^-7 mol/（m^2.s.Pa） at 200 ℃ and 0.3 MPa. The permselectivity of He with respect to CO2, O2, N2, CH4 and SF6 was 98, 49, 64, 79 and 91, respectively, indicating a molecular sieving effect. The calcination temperature played a key role in determination of the hydrothermal stability of microporous silica membrane, which was confirmed experimentally. The performance of SiO2 membrane calcined at 400, 600 and 800℃ deteriorated under the H2O pressures of 8, 200 and 200 kPa, respectively.