超稀溶液体系中高性能MFI型沸石膜的制备及表征

以廉价管状大孔α-Al₂O₃作为载体, 采用二次生长法, 在超稀溶液体系(H₂O/SiO₂=1000)中成功制备了高性能MFI型沸石膜, 分别考察晶种尺寸和H₂O/SiO₂对沸石膜的形貌及渗透蒸发性能的影响。结果表明, 尺寸为0.4 μm晶种制备的晶种层具有更大的晶核密度, 能够增加载体表面的成核位点, 因此对沸石膜的生长具有更强的诱导作用。超稀溶液体系中低浓度的模板剂和硅源环境能够控制沸石晶体的生长速率, 从而降低沸石膜厚度, 同时可以抑制晶间缺陷的形成。将制备的沸石膜用于60℃渗透蒸发分离5wt%乙醇/水混合物, 分离因子α_(乙醇/水)和渗透通量分别为47和4.09 kg/(m²·h)。采用超稀的合成液配方和廉价大孔载体, 既可以降低沸石膜制备的原料成本, 又可以提高沸石膜的渗透通量, 显示出MFI型沸石膜在脱除水中低浓度有机物潜在的工业化应用前景。

Preparation and Characterization of High Performance MFI Zeolite Membrane in Ultradilute Solution

High performance MFI-type zeolite membrane was successfully prepared in ultradilute solution (H₂O/SiO₂= 1000) on inexpensive and macroporous α-Al₂O₃ tubular support by secondary growth. Influences of seed size and H₂O/SiO₂ on morphology and pervaporation performance of the zeolite membranes were investigated. Results showed that the seed layer prepared with 0.4 μm seeds had higher crystal nucleus density which could increase the amount of the nucleation site on the support surface, resulting in a stronger induced effect on the growth of zeolite membrane. The low-concentration template and silicon source in ultradilute solution decreased the growth rate of zeolite crystals, which could reduce the zeolite membrane thickness and effectively inhibited the formation of intercrystalline defects. The flux and separation factor (α_{ethanol/water}) of the resulting MFI zeolite membrane achieved 4.09 kg/(m²·h¹) and 47, respectively, for separation of 5wt% ethanol/water mixture at 60℃. Ultradilute solution and low-cost macroporous α-Al₂O₃ tubular support reduced the preparation cost of MFI zeolite membranes and increased the flux, showing prospect of the potential industrial application of MFI-type zeolite membrane for removal of the low-concentration organic compounds in water.