Synthesis and gas permeation properties of silicalite-1 zeolite membrane

Silicalite-1/ceramic composite membrane was prepared on the outer surface of the alpha-Al2O3 tubular support by in-situ hydrothermal synthesis. The membrane was characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The pure gas permeances of H-2, N-2, Ar, CH4, C2H4, C2H6, C3H8, n-C4H10 and i-C4H10 were measured as a function of the pressure difference at 298 and 473 K. The permeances of H-2, N-2 and Ar showed little dependence on the pressure differences; the permselectivities of H-2/i-C4H10 were 249 and 36.2 at 298 and 473 K respectively, which is a characteristic of molecular transport in silicalite-l channels. The permeances of light alkanes decreased in the following order: CH4 > C2H6 > C3H8 > n-C4H10 > i-C4H10. The permselectivity of n-C4H10/i-C4H10 was above 15 at 298 K. As the temperature increased, the permeances of all gases increased except those of N-2 and Ar, and a significant increment was found for alkanes. The permselectivity of n-C4H10/i-C4H10 decreased to about 9 at 473 K. The gas permeation results showed that the silicalite-1/ceramic composite membrane was defect-free.