在粗孔a-Al_2O_3载体上合成NaA沸石膜

采用稀释的水玻璃作为分散介质配成0.5%(w)的NaA沸石悬浮液,对粗孔a-Al2O3(孔径3~5 mm)载体管修饰并预涂晶种,进一步采取原位水热晶化法在a-Al2O3载体管外表面制备NaA沸石膜. 重复合成5次后,在载体表面形成一层致密、连续的沸石晶体层. 由XRD确定该晶体为A型沸石,由SEM可观察到膜厚约15~20 mm,膜表面上的沸石晶体大小约为3~5 mm,晶体之间紧密孪生在一起,看不出晶间空隙. 制备的NaA沸石膜的H2渗透率为3.0510-6 mol/(m2sPa), 对H2/N2和H2/C3H8的理想分离因数分别为6.9和15.6,超过对应的努森扩散值3.74和4.69,说明所制备的NaA沸石膜具有分子筛分性能.

Preparation of Zeolite NaA Membrane on Rough Porous a-Al_2O_3 Tube

Zeolite NaA membrane was prepared hydrothermally on the outer-surface of a porous a-alumina tube (pore size of 3~5 mm) using a gel with the composition of SiO2:Al2O3:Na2O:H2O=2:1:2:200 (mole ratio). Before the hydrothermal reaction, the support was seeded with NaA zeolite, which was already dispersed in diluted water glass. After several hydrothermal synthesis steps, a dense intergrown zeolite crystal layer about 15~20 mm in thickness was formed on the outer surface. The zeolite crystals were about 3~5 mm in size and there was no apparent cracks between them, as observed from SEM images and permeation measurement. The permeance of H2 and N2 was 3.0510-6 and 4.410-7 mol/(m2sPa), respectively. The permselectivity of H2/N2 and H2/C3H8 was 6.9 and 15.6 under room temperature, higher than the respective Knudsen diffusion ratio of 3.74 and 4.69.