制备条件对Ge掺杂二氧化硅膜溶胶粒径和氢气渗透与分离性能的影响

Effect of Ge-doped silica membrane preparation conditions on the sol particle size and hydrogen permeation and separation performance

以正硅酸乙酯(TEOS)和乙氧基锗(Ge(OC2H5)4)为前驱体通过溶胶-凝胶法制备Ge掺杂的二氧化硅溶胶,采用浸渍提拉法在γ-Al2O3/α-Al2O3多孔陶瓷支撑体上成膜,通过动态光散射(DLS)技术和气体渗透法,研究制备条件对Ge掺杂二氧化硅膜溶胶粒径和氢气渗透与分离性能的影响.结果表明溶胶胶粒随着温度、Ge的掺杂量、醇比例的增大而变大,且分布变宽;随着硝酸比例的增大呈现先减小后增大的趋势,在HNO3/TEOS=0.085时达到最小.溶胶粒径平均大小从2.3nm到91nm时H2的渗透率从4.4×10-7 mol/(m2.s.Pa)上升到8.2×10-7 mol/(m2.s.Pa),H2和CO2的通过率都随着胶粒的增大而呈增大的趋势;但是气体的分离系数呈减小的趋势,只有溶胶胶粒平均值小于4.5nm的溶胶涂膜后,才具有分子筛分效应,其H2/CO2值大于努森扩散的理想分离系数.

Ge-doped silica membranes were prepared by the co-hydrolysis and condensation of tetraethyl orthosilicate（TEOS） and ethoxy-germanium Ge （OC2 H5）4 under different conditions. The effect of synthesis conditions on the particle size of Lie-doped silica sol ana tile nyarogen permeanon ana separanon performance of the silica membranes derived from sol with different particle size were investigated in detail by dynamic light scattering and gas permeation measurement respectively. The results show the sol particle size increases with increasing in the amount of Ge（OC2 Hs）4 doped and the temperatures. Increasing in the acidic concentration leads to a decrease of sol particle size when the molar ratio of HNO3/TEOS is lower than 0. 085, however, further increasing the molar ratio of HNO3/EtOH results in an increase in sol particle size. The sol particle size deceases with increasing in molar ratio of H20/EtOH. Both permeance o{ H2 and CO2 increases with increasing in sol particle size, from 4. 4X 10-7 mol/（m2 · s · Pa） at a particle size of 2. 3 nm to 8. 2×10-7mol/（m2 · s · Pa） at a particle size of 90 nm for hydrogen. However, only membranes derived from sol with a size less than 4. 5 nm exhibit a H2/CO2 permselectivity higher than that of Knuden diffusion.