Preparation And Pervaporation Performence Of ZSM-5 Zeolite Membranes

Pervaporation as a novel membrane separation technology, has been found wide applications in chemical industry, and exhibits some advantages such as high efficiency, less pollution and low energy consumption. Zeolite membranes are regarded as the potential membrane materials for pervaporation due to their very uniform and regular pore size, high chemical resistance and good thermal, chemical and mechanical stabilities, which have attracted considerable attention. ZSM-5 zeolite membranes with regular channels of 0.5～0.6 nm and Si/Al ratio of 10～∞ in framework have been considered as promising candidates to achieve highly water-selective performance for dehydration of organics under acid conditions.In this work, the ZSM-5 zeolite crystals and membranes were prepared by different routes. The effects of stirring and aging temperature on the membrane morphology and separation performance were investigated. The main research contents and results are as follows:(1) The effects of crystallization time, alkali and water content in the synthesis solution on the crystallinity, size and Si/Al ratio of ZSM-5 crystals were researched. ZSM-5 crystals with few impurities were synthesized from template-free gel of composition 0.20 Na2O:SiO2: 0.017 Al2O3:43.7 H2O. The products gained from template-free and seed-sssisted synthesis route have higher crystallinity and lower Si/Al ratio.(2) ZSM-5 membranes were prepared on cheap coarse porous α-Al2O3 tubes by secondary crystallization method.The effects of different synthetic routes, string and aging temperature on the membrane morphology and separation performance were researched. High performance ZSM-5 membranes with low Si/Al ratio and the thickness of 3 μm were synthesized from organic template-free synthesis solution at tring temperature of 30 ℃ and aging temperature 20 ℃. The as-sythesized ZSM-5 membranes displayed good pervaporation performances for dehydration of 90 wt.% AcOH/H2O and IPA/H2O mixtures, and the permeate fluxes were 0.65 kg·m-2·h-1 and 2.78 kg·m-2·h-1 and corresponding separation factors were 547 and 6129 at 75 ℃, respectively.