| In this paper, in order to improve the pervaporation performance of the Silicalite-1membrane and to meet the demand of industrial production, synthesis of Silicalite-1zeolite membranes is investigated. In addition, the stainless-steel-net-supported new structured Silicalite-1membranes are synthesized by hydrothermal synthesis. The main achievements are as follows:(1) By using "PVA-assisted seeding method", the large defects on the surface of alumina substrate can be well blocked by dip-coating into zeolite seed suspension containing a small amount of PVA (e.g.2wt.%).(2) The silicalite-1membranes on the seeded support by PVA-assisted seeding are synthesized from the synthesis solution with molar composition of1TEOS:0.17TPAOH:120H2O by two stages varying temperature crystallization, namely at120℃for low-temperature crystallization, followed by crystallization at175℃for24h. The effect of crystallization time at120℃on the membrane performance is investigated. The membrane synthesized at120℃for2h shows the improved PV performance for5wt.%ethanol/water mixture at60℃.(3) B-silicalite-1membrane shows the better compactness than that of the Silicalite-1membrane. The silicalite-1membrane synthesized from the synthesis solution with molar composition of1TEOS:0.17TPAOH:0.03B(OH)3:120H2O by two stages varying temperature crystallization, namely at120℃for1h and at175℃for24h, shows the better PV performance for5wt.%ethanol/water mixture at60℃.(4) For the425-mesh stainless-steel-net, silicalite-1membranes are synthesized in the synthesis solution of1TEOS:0.17TPAOH:120H2O by repeated in-situ hydrothermal growth. For the800-mesh stainless-steel-net, silicalite-1membrane by secondary hydrothermal growth using dense gel dip-coating method and wet-rubbing method with seed and by in-situ two stage varying temperature hydrothermal growth were used to prepare compact zeolite membranes. The repeated in-situ hydrothermal growth led to formation of a compact and dense and continuous silicalite-1membrane. |
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