Preparation of NaA zeolite membranes using poly(ethyleneimine) as buffer layer, and study of their permeation behavior

Zeolite NaA membranes were prepared hydrothermally by secondary crystallization process at different temperatures (55 degrees C75 degrees C) on porous a-alumina-based support tubes (inner side) precoated with poly(ethyleneimine) (PEI) buffer layer and NaA seed particles. The NaA seed crystals synthesized at 65 degrees C/2 h in the size range 100200 nm having BET surface area of 71.57 m2g-1 were used for secondary crystallization of the membranes. The secondary crystallization at 65 degrees C for (4 + 4) h (double-stage) showed highly dense NaA grains in the microstructure of the membrane with a thickness of 5 mu m. It rendered the permeance values of 50.6 x 10-8, 2.47 x 10-8, and 0.55 x 10-8 molm-2s-1Pa-1 for H2, N2, and CO2, respectively, with their permselectivity of 20.48 (H2/N2), 92 (H2/CO2), and 4.49 (N2/CO2). A tentative mechanism was illustrated for the interaction of PEI with the support substrate and NaA seed crystals