二次生长法FAU型沸石膜的合成与表征

Synthesis and characterization of FAU zeolite membrane on seeded substrate

采用二次生长成膜的方法，在合成液的配比为46Na2O：12．8SiO2：1Al2O3：4 500H2O的稀溶液中，在大孔a—Al2O3陶瓷管载体外表面，合成出致密的FAU型沸石膜，并用扫描电镜、X射线衍射以及气体渗透性能等手段对沸石膜进行了表征．用热浸渍法将与载体孔径尺寸相近的晶种引入载体表面，晶种嵌入了载体表面的孔口和次孔口，且均匀地分布在膜管表面，明显改善了载体的表面性质，促进了膜的生长．所制备的膜表面晶粒相互交织生长完好，致密，连续，规整，无裂缺，沸石膜厚约6～7μm．H2的渗透率为1．46×10^-6mol／（m^2·s·Pa），H／SF6的理想分离因子为9．67，高于其努森扩散值8．54．对稀溶液中沸石膜的形成机制也进行了探讨．

Continuous ultra fine crystal FAU membranes were synthesized hydrothermally on the outer surface of - alumina support tube （ 12 mm o. d, and 8 mm i. d. ）. The molar composition of the starting gel was 46Na2O： 12.8SiO2 ： 1Al2O3 ： 4 500H2O. Surface - modified tubes were seeded with zeolite X crystals prior to membrane synthesis. The seed layer with uniform crystal size that was as larger as the average pore diameter of the alumina supports on the substrate favored the formation of a continuous top - layer zeolite membrane during the growth. The substrate surface was improved significantly, and a uniform and smooth seed layer was formed by seeding. The outer surface of the tube is completely covered with zeolite crystals and the thickness of the membrane is about 6-7 μm. The measured permeability of H2 is about 1.46 × 10^-6 mol/（m2 ·s·Pa）, and the ideal selectivity of H2/SF6 is 9.67, which is higher than the respective Knudsen diffusion ratio of 8.54. The mechanism of membrane formation was investigated.