Preparation And Pervaporation Application Of Zeolite T Membrane

Dehydration of organics for highly purified organic products is essential in the fine chemicals, petrochemical and pharmaceutical chemicals. The conventional separation process is energy intensive and low efficiency. Pervaporation is considered as the potential technology to replace conventional separation process, because of it’s high separation efficiency, low energy consumption, and low pollution. Dehydration of a large varieties of organic liquids in the actual industrial applications is under acidic conditions, such as purification of ethanol and isopropanol used as solvents in pharmaceutical chemicals and dehydration of ester products. Zeolite NaA membranes have become ideal materials on dehydration of organic by pervaporation due to its high hydrophilicity. However, zeolite NaA membranes can not be applied for dehydration of organic liquids containing an acid because of their instability in acidic media. Zeolite T membrane is acid-resistant while remaining hydrophilic, which has excellent pervaporation performance for dehydration of organic liquids. Zeolite T membrane has the potential for dehydration of organic by pervaporation in the presence of organic acid, such as esterification hybrid process and alcohol dehydration in fermentation engineering. Therefore, zeolite T membrane has a very broad application prospect. However, it’s found that mature preparation routes are still the urgent problems in study of zeolite T membrane.Secondary growth method is composed of deposition of zeolite seed crystals to form a seed layer and then crystallization of the seeded support to form a polycrystalline zeolite layer. The high quality of seed layer is the key to prepare high quality zeolite membranes by secondary growth method. So, seeding technology has become one of the hot spots. Microwave hydrothermal method is becoming the popular method for preparation of zeolite membranes in the recent years. It can shorten the synthetic time effectively, and the membrane prepared by microwave heating is thin and compact, and permeation performance has been improved.Based on the above research ideas, this paper firstly explored different sizes of zeolite T were synthesized to modify the support surface and be used as seeds. Then, zeolite T membranes were prepared by conventional hydrothermal method in gel solutions and microwave hydrothermal method in clear solutions respectively, to explore the mature preparation routes. Also, an effective seeding method was designed on the inexpensive macroporous support. The as-synthesized zeolite T membranes were characterized by X-ray diffraction(XRD) and scanning electron microscope(SEM). The main research results are briefly introduced as follows:(1) Zeolite T with4～6μm was synthesized by the formulation25SiO2:l Al2O3:6.5Na2O:2.25K2O:350H2O. Different sizes of zeolite T were synthesized by changing synthesis conditions with the formulation18.2SiO2:1Al2O3:4.2Na2O:1.5K2O:0.82TMAOH:212.7H2O.(2) Zeolite T membrane was synthesized by conventional heating in gel solutions. The influence of synthesis conditions were investigated. When zeolite T membrane was synthesized under conditions that include n(Na2O+K2O)/n(SiO2)=0.35, n(H2O)/n(SiO2)=30,373K and30h, the performance of as-synthesized membranes for90wt.%ethanol/water mixture was high with the flux up to1.67kg·m-2·h-1and the separation factor of1115.(3) The high quality of seed layer was obtained by two-stage varying-temperature hot dip-coating seeding method on the inexpensive macroporous support. The as-synthesized membranes have high performance with the water flux up to2.12kg·m-2·h-1and the separation factor was more than1000. The two-stage varying-temperature hot dip-coating seeding method has good reproducibility. The pervaporation performance of as-synthesized membrane was studied in detail.(4) Zeolite T membrane was synthesized by microwave heating in clear solutions. The influence of synthesis conditions were investigated. The as-synthesized membranes have high performance with the water flux up to1.36kg·m-2·h-1and the separation factor was more than1000at348K.