Synthesis Of Stainless-steel-net Supported Silicalite-1 Molecular Sieve Membrane For Separating Ethanol From Water

Silicalite-1 zeolite membrane, a kind of inorganic membrane, has good heat resistance, acid resistance and hydrophobicity, thanks to the infinite silicon aluminum ratio, which deserves the very good application prospect of removal of organic compound from water, especially in situ removal of ethyl alcohol from fermentation, thus achieving continuous production of fuel ethanol.At present, Silicalite-1 zeolite membranes mostly is synthesized on the aluminiferous tubular support. However the flux was low. What’s more, when loaded into the membrane module, the space utilization rate is even lower. The stainless steel net not only has high porosity, but also has soft texture and can be processed into scroll type membrane module, so as to improve space utilization. In this paper, inexpensive stainless steel mesh is used as the support, Silicalite-1 zeolite membrane with good compactness, certain separation performance and higher flux than traditional tubular supported membrane is prepared. The main conclusions of this paper are as follows:(1) The effects of crystallization temperature, crystallization time, water content, fluid level of synthesis solution, content of TPAOH, and so on, on the membrane morphology are investigated. When crystallization temperature kept at 175 ℃, water content following the mole ratio of 1TEOS:0.17TPAOH:80-160 H2O, crystallization time in 2-5 days, the depth of synthesis solution being about 0.05 m, It is easier to obtain compactness membrane.(2) It is difficulty to seed into the stainless steel mesh support by common impregnation method, so repetition synthesis for twice is conducted, which can shorten the crystallization time to a certain extent.(3) The effects of water content, crystallization time and aperture of stainless steel mesh on pervaporation performance of Silicalite-1 zeolite membrane are investigated. When the water content is in a certain range, the longer the crystallization time is and the bigger aperture of stainless steel mesh is, the bigger the separation factor is and the lower the flux. In order to achieve good pervaporation performance, water content should follow the mole ratio of 1 TEOS:0.17 TPAOH:100-120 H2O, and crystallization time should be in 2-3 days. The best overall performance is obtained with the 7.28 kg-m■2■h-1 for flux and 15.47 for the separation factor.(4) The effects of content F- on pervaporation performance of Silicalite-1 zeolite membrane are investigated. In order to achieve good pervaporation performance, content of F" follow the mole ratio of 1 TEOS:0.17 TPAOH:100 H2O:0-0.12 NaF. When the content of F" was 0.12, the flux reach 6.76 kg■m-2■h-1, with 20.49 for the separation factor.(5) The effects of feed concentration and temperature on the pervaporation performance of Silicalite-1 zeolite membrane are investigated. In low ethanol concentration range (5-25wt.% EtOH), with increasing of ethanol concentration, the separation factor decreases gradually, but the flux changes slightly. With temperature of feed rising from 30 ℃ to 75 ℃, the flux increases gradually, while the separation factor decreases.