Preparation And Permeation Properties Of PHI Zeolite Membrane

Zeolite membranes have advantages such as precisely defined pore structure and highstability, which could enable applications in gas or liquid separations, catalytic membranereactors, and ion exchangers. PHI zeolite membranes belong to the low-silica8MR group andhave a higher acid-stability and higher hydrophilicity.In this study, various influence factors have been investigated and optimized during thesynthesis process of PHI zeolite membrane. The as-synthesized sample was characterized byX-ray diffraction (XRD), scanning electron microscopy (SEM) and pervaporation tests (PV).The main work of this thesis is as followed:1. PHI zeolite membrane was synthesized on the α-Al2O3disk by in-situ method with asynthesis solution molar ratio of Na2O:K2O:SiO2:Al2O3:H2O=1.5:0.25:4.87:1:101in a Teflonlined autoclave in a static condition. Influences of crystallization temperature and time on thesynthesis of PHI zeolite membrane were investigated. XRD, SEM and PV results show thatthe best condition by in-situ method is150℃,8h.2. PHI zeolite membranes have been prepared by secondary growth method on thesurface of porous α-Al2O3disk support. Influences of the preparation method of the zeoliteseed, secondary growth time and temperature on membrane synthesis were investigated. Theas-synthesized PHI zeolite membranes were characterized by X-ray diffraction (XRD) andscanning electron microscopy (SEM). The XRD results show that PHI zeolite emerges on thesupport. The SEM results show that the support surface is fully covered by uniform andcompact PHI zeolite membrane synthesized by secondary growth method and the thicknessesof the membrane layer is about20μm.The as-synthesized PHI zeolite membranes were used for dehydration of methanol(MeOH), ethanol (EtOH), isopropanol (IPA) and tert-butanol (TBA) solutions with differentkinetic diameters. The influences of feed concentration on separation performance wereinvestigated by pervaporation tests. Results show that PHI membranes exhibited excellentperformance for the dehydration of alcohol/water mixture. It was found that the flux and theseparation factors of isopropanol and tert-butanol increased with the increment of the wateramount in the feed, instead, the separation factors of methanol and ethanol decreased slightly.