| Zeolite membranes with uniform, molecular-sized pores have potential applications in separation of different substances at molecular levels under the circumstances of high-temperature, chemical and biological corrosions and in integration of catalysis and separation processes for many fields such as environmental protection, petrochemical and biochemical industry. Silicalite-1 membrane with pore size similar to that of industrially important light substances possesses potential applications in separation of organics from water and catalytic membrane reactors operated in severe conditions. Researches on the development of high performance Silicalite-1 membrane and its applications in renewable fermentation product fuel ethyl alcohol are of piratical and scientific significance.The secondary growth method is applied to synthesis Silicalite-1 membranes on the macroporous a-Al2O3 supports. The effects of seed size, the crystallization temperature, the support nature on the morphorgy and separation performance of the obtained Silicalite-1 membranes are investigated. And the optimized synthesis parameters are established. The membrane synthesized at 175℃for 48h with crystal seeds of 500nm and the composition of synthesis solution of 0.1TPAOH:1TEOS:90H2O showed the highest ideal separation factor of H2/SF6 of 72.2 with H2 permeance of 8.6×10-7mol·m-2·s-1·Pa-1 and best pervaporation performance with separation factor of ethanol over water of 51.1, permeation flux of 0.82kg·m-2·h-1 for 5 wt.% ethanol aqueous solution.A two-stage-varying temperature synthesis (TSVT) was applied to synthesize zeolite Silicalite-1 membrane supported on the stainless steel tube. TSVT synthesis is carried out at low temperature, to promote nucleation, after which the temperature is rapidly increased, to promote crystal growth. The effect of the synthesis temperature and the crystallization time on the membrane performance was investigated. The membranes by TSVT method gave a much higher flux and separation factor at the same operation condition than those by constant temperature synthesis. At lower second stage temperature and with low water content in the synthesis mixture, the membrane shows a high pervaporation flux of 2.80kg·m-2·h-1 with comparable separation factor of 34.3 at ethanol content of 5wt.% and 60℃.Cheap Sn was adopted to isomorphously substitute Si and Sn-ZSM-5 zeolite membrane on Al2O3 support was first prepared aiming at improving separation factor of ethanol over water by secondary growth method. The pervaporation characterization of Sn-ZSM-5 zeolites are performed in order to determine the synthesis conditions of Sn-ZSM5 membranes. The effects of Si/Sn ratio, seed size, the crystallization temperature, the support nature on the morphorgy and separation performance of the resulting Sn-ZSM-5 membranes are investigated. The Sn-ZSM5 membranes showed a separation factor of 18.7 for 4.52wt.% ethanol aqueous solution, low than that of silicalite-1 membranes.The pervaporation performance of the Sn-ZSM-5 membrane using acetic acid aqueous solution was examined. The Sn-ZSm-5 membranes were more effective for separation of acetic acid from water than silicalite-1 membranes. The effects of Si/Sn ratio, temperature, feed concentration on separation performance were investigated. The separation factor of acetic acid to water increased with decreasing Si/Sn ratio though the total flux decreased relatively. The separation factor increased with the temperature in the range 30 - 90℃. The Sn-ZSM-5 membrane with Si/Sn = 25 had separation factor of 7.8 and a total flux of 0.49 kg·m-2·h-1 for a 5 wt. % acetic acid aqueous solution at 90℃, while the sililicalite-1 membrane showed separation factor less than 1.5 at the same operation conditions. Detailed discussion is made on the possible reasons of the obtained different separation selectivity.A novel hydrophobic Silicalite-1/polydimethylsiloxane (PDMS) composite membrane was prepared in order to achieve high performance for pervaporation of ethanol form water. PDMS layer thickness was controlled by PDMS concentration. The influence of Silicalite-1 and PDMS layers on the the pervaporation performance of composite membrane were investigated. The composite membrane showed a high permeation flux and selectivity of ethanol over water and its stability was preferable. The composite membrane gave much improved separation performance with a flux of 2.67kg·m-2·h-1 and separation factor of 54.9 at the ethanol content of 5wt. % and 60℃.
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