Synthesis of zeolite NaA membranes with high permeance under microwave radiation on mesoporous-layer-modified macroporous substrates for gas separation

This article reported the NaA zeolite membranes with high permeance synthesized with microwave heating method under different conditions: (I) on a macroporous substrate in gel, (II) on a mesoporous/macroporous (top-mesoporous-layer-modified macroporous) substrate in gel, and (III) on a mesoporous/macroporous substrate in sol. In general, the H2 permeance of the NaA membranes by microwave heating in gel was usually at the level of 10−6 mol s−1 m−2 Pa−1, much higher than that by the conventional hydrothermal synthesis. At similar H2/C3H8 permselectivity. On the substrate modified mesoporous toplayer, the H2 permeance of the NaA membranes by microwave heating in gel or sol was further enhanced, while maintaining comparable H2/C3H8 permselectivity, due to the prevention of penetration of the reagent into the pores of the macroporous substrate. Meanwhile, the synthesis took less time in sol than in gel on the mesoporous/macroporous substrate. The NaA membranes synthesized in sol had larger permeance than those in gel and underwent transformation in shorter time. The permeation of C3H8 suggested that there existed unwanted intercrystalline pores or defects in the membranes.