Synthesis and pervaporation properties of NaA zeolite membranes prepared with vacuum-assisted method

摘要

Uniform and dense NaA zeolite membranes were synthesized on the tubular alpha-Al2O3 support with a vacuum-assisted method by using low vacuum. The effect of vacuum degree on the formation of the NaA zeolite membrane was investigated. With the assistance of the vacuum, the negative influence of the gravitation force could be effectively reduced. Therefore, the zeolite particles could transport to cover the entire area of the support surface homogeneously, which facilitated formation of uniform and dense zeolite membranes. With the assistance of the vacuum, most zeolite particles migrated to the support surface for membrane formation, and the amount of crystals forming in the liquid phase could be greatly reduced. In addition, zeolite particles could be transported to the support surface rapidly, increasing the rate of dense membrane formation. The pervaporation properties of the as-synthesized zeolite membranes were evaluated by dehydration of 95wt.% isopropanol/water mixtures at 343 K. The as-synthesized NaA zeolite membrane prepared with the vacuum-assisted method (i.e., with the assistance of l0mmHg vacuum degrees), showed good pervaporation properties. The separation factor (water/isopropanol) was 3781 and the flux was 1.49kg/m2h, respectively. Based on the observed results, the formation mechanism of zeolite membrane with vacuum-assisted method was discussed.