Preparation of high-permeance MFI membrane with the modified secondary growth method on the macroporous α-alumina tubular support

MFI membrane with high permeance was successfully synthesized on the macroporous (pore size of 3–4 μm) α-Al2O3 tubular support with a novel modified secondary growth method. Before the crystallization, the seeded support was wrapped with Teflon tape in order to focalize the growth of crystals in the region of seed layer. The as-synthesized membrane was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and single-gas permeation testing. The results indicated that the as-synthesized membrane had a thickness of 6–8 μm similar to the thickness of the seed layer and exhibited high gas permeance. At room temperature, the permeance of H2 and the ideal separation factor of H2/SF6 reached 1.64 × 10−6 mol m−2 s−1 Pa−1 and 71, respectively. The permeance of single-gas increased with the increasing of temperature. The ideal separation factors of H2/i-C4H10 and H2/SF6 decreased with the increasing of temperature from 298 to 473 K. At 473 K, the ideal separation factors of H2/i-C4H10 and H2/SF6 were 12.16 and 11.08, which were still higher than their Knudsen ratios of 5.39 and 8.54, respectively.