Vapor-phase transport of MFI nanosheets for the fabrication of ultrathin b-axis oriented zeolite membranes
Ultra-thin and b-axis oriented MFI zeolite membranes were fabricated by a vapor phase transport(VPT)method using ethylenediamine-water vapor.The membrane thickness was rationally controlled by converting a deposit layer of MFI nanosheets into a dense zeolite membrane.Scanning electron microscope and X-ray diffraction results revealed that the prepared membrane had a thickness of about 280 nm with a highly b-axis oriented dense structure.The binary gas separation test of butane isomers showed that a permeation rate of n-butane of 1.5×1 0-7 mol·m-2·s-1·Pa-1 at a separation factor of 14.8 could be achieved for an equimolar n-butane/iso-butane mixtures at 333 K.Na2SiO3,serving as a source of silica and alkalinity,played a crucial role in the secondary growth of MFI zeolite nanosheets.Na2SiO3 facilitated the fusion growth among the MFI zeolite nanosheets in the presence of amine vapor,which improved the orientation and compactness of the membranes.
membrane separationMFI zeolite nanosheetvapor phase transport methodoligomeric silicon sourcesodium silicate
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