Template-free Synthesis And Performance Study Of MFI-type Zeolite Membranes

Zeolite membranes not only have large permeating flux, but also demomstratehigh selectivity to specific species for gas and liquid mixtures due to the molecularsieving effect of individual zeolite crystals together with selective adsorptionproperties. They are ideal membrane materials to achieve high permeation flux whilekeeping selectivity satisfactory. In addition, because of their good chemical andthermal stabilities, zeolite membranes are aslo good candidates for catalyticmembrane reactors. Up to present, zeolite membranes have been widely applied in thefields such as membrane separation and/or catalysis, chemical sensors, electrodes, Therelevant research has attracted the attention in the scientific communities.This thesis is to prepare MFI type zeolite membranes by template-free andtemplate methods, and inspect the influence of the silicon source on the membranequality, examines the pervaporation performances of the synthesized zeolitemembranes, and explore appropriate template-free sysnthesis conditions. With respectto the b-oriented zeolite membrane by the template-free method, the EDX analysisshows the Si/Al ratio is about1, the aluminum element in the alumina substratepermeated into the membrane. For the MFI-type zeolite membrane synthesized by thetemplated method, the EPMA analysis indicates that the Si/Al ratio is more than2000.According to the pervaporation test for5wt.%ethanol aqueous soloution at40℃, theb-oriented zeolite membranes by the template-free method does not have selectivepermeation characteristic for ethanol, the separation factor is~1. Whereas, theseparation factor has reached to15.2for the zeolite membrane synthesized by thetemplated method. The presence of defects and surface hydrophobicity determine thepervaporation performance for selective separation of ethanol. Obviously, thehydrophobic zeolite membranes have the ability to selectively separate ethanol fromits aqueous solution. The hydorphillic zeolite membranes, even if there are no defects,do not have the selective permeating behavior for ethanol.