Influence of sodium ion on high-silica SSZ-13 membranes for efficient CO2/CH4 and N2/CH4 separations

Here, high-silica SSZ-13 membranes were prepared on macroporous supports by regulating sodium sources (NaOH, NaCl, Na 2 SO 4 and sodium-free) under fluoride and aluminum free gel. A pure phase and high gas permeation SSZ-13 membrane with oval-shaped crystals on the membrane surface was obtained by NaCl. It suggests that alkali metal sodium ion promoted crystal crystallization. The influence of Na 2 O (2NaCl)/SiO 2 ratio (from 0.025 to 0.2) on the crystallization process of zeolite membranes was investigated in detail by XRD , SEM and gas permeation tests. The content of NaCl hardly affected the structure of SSZ-13 but could affect the morphology and size of the crystals. The best membrane (NaCl/SiO 2  = 0.2) had a mixed CO 2 and N 2 gas permeance of 5.4 × 10 −7  mol/(m 2 s Pa) and 5.2 × 10 −8  mol/(m 2 s Pa), along with the CO 2 /CH 4 and N 2 /CH 4 selectivity of 155 and 12.3, respectively. The effects of pressure drop, temperature and feed concentration on membrane separation performance were explored. In addition, the obtained SSZ-13 membrane exhibited the hydrothermal stability in the humid N 2 /CH 4 mixture under 298K, indicating the application prospects in natural gas separation.