The formation mechanism of ZSM-5 zeolite membranes

Continuous ZSM-5 zeolite membranes have been prepared by multi in-situ crystallization (MISC) and temperature-varying hydrothermal synthesis (TVHS), respectively. The membrane formation process was discussed, and the formation mechanism was proposed. During MISC under constant temperature, the crystals formed in the last synthesis grew discontinuously; they would dissolve first and thus induce more nuclei to form. At last, all nuclei grow together into integral zeolite membranes. For TVHS, crystals on the support grew into large ones by a re-nucleation and re-growth process on the crystal surface, in this way the final crystals lost their typical morphology and the intercrystalline gaps disappeared, and the dense membrane was formed.