The mordenite membrane was prepared on a α-Al 2O 3 tube by in situ hydrothermal synthesis. The crystallization was carried out at 443 K for 2～4 days. Silica sol and sodium aluminate were used as the sources of silica and alumina, respectively, and tetraethylammonium bromide (TEABr) as the template. The molar composition of the parent solution was 11 4Na 2O∶1 0Al 2O 3∶40SiO 2∶2500H 2O∶1 5TEABr. SEM and XRD were used to characterize the powder product and the composite membrane. The synthesized mordenite membrane proved to be in a full coverage and an excellent intergrowth. The mordenite crystals were about 20～30 μm and the thickness of the mordenite membrane was 30～40 μm. Based on the SEM pictures of the membrane in the early stage of hydrothermal synthesis, a growth model for the mordenite membrane was assumed. At first a gel layer was formed on the surface of the alumina tube. Nucleation took place in the gel layer but not at the interface of the gel layer and bulk solution. The gel layer provided the nutrients for the growth of zeolite crystals. After the gel layer was consumed completely, the zeolite crystals or membrane were exposed to the bulk solution. The membrane separation test on the mordenite membrane showed that the permeances of pure H 2 and N 2 at 298 K were 6 92×10 -7 and 1 81×10 -7 mol/(m 2·s·Pa), respectively. The ideal selectivity of H 2/N 2 was 3 82, which is higher than that of Knudsen mechanism. It suggested that the mordenite membrane had the ability of molecular sieving.
