Gel-less steam-assisted crystallization of platelike MFI crystals for the fabrication of b-oriented zeolite membranes

Novel platelike MFI zeolite crystals were used as seeds to fabricate dense and flat MFI zeolite membranes with b-axis orientation on porous sintered quartz wool discs through a gel. free steam. assisted crystallization (GLSAC) method. Firstly, the platelike MFI crystals were coated on the porous support by a filtration method. Then the seeded support was dipped in a tetrapropylammonium hydroxide (TPAOH) aqueous solution followed by a drying step. Subsequently, the dried discs were heated in an autoclave with a small amount of water at the bottom to grow into continuous membranes. Influences of the TPAOH concentration, water at the autoclave bottom, temperature, and time on the MFI zeolite membranes were investigated. The results of the scanning electron microscope and X-ray diffraction show that the out-plane growth of the platelike MFI seeds was suppressed at an optimized TPAOH concentration and water content. A dense and flat MFI zeolite membrane with a thickness of about 750 nm was successfully prepared. Binary butane isomers separation tests revealed that a separation factor (SFA/B) of 36 at a permeation rate of 1.5x10(-7) mol.m(-2).s(-1).Pa-1 for n-butane was achieved.