【作者】 孙维国；

【导师】 王金渠；

【作者基本信息】 大连理工大学 ， 化学工艺， 2009， 博士

【摘要】 MFI型沸石膜（Silicalite-1和ZSM-5两类）具有与分子尺寸相近的孔道体系,能耐高温、化学及生物侵蚀,可在分子级别上进行物质分离,实现催化反应分离一体化,在环保、石油化工、生物化工等领域具有广泛的应用。开展高性能MFI型沸石膜的制备研究,并将其应用于渗透汽化生物质燃料乙醇的分离和水中分离乙酸,具有重要的应用价值和科学意义。采用二次生长法在大孔载体上合成Silicalite-1沸石膜,考察了晶种的大小、涂晶种方法对膜的厚度和成膜性能的影响。研究结果表明,当合成液的配比为0.1TPAOH:1TEOS:90H₂O,晶化时间48h,晶化温度175℃,晶种粒径为0.5μm时,所得到的膜对H₂的渗透率为8.6×10^-7mol·m^-2s^-1·pa^-1,H₂/SF₆的理想分离系数最高为72.2,对5wt.%的乙醇/水体系渗透汽化分离系数达到了51.1,渗透通量达到0.82kg·m^-2·h^-1。利用低温利于成核高温利于晶体生长的原理,采用两步变温合成法在不锈钢载体上合成Silicalite-1膜,且优化了合成条件。在水硅比低、二段晶化温度高的条件下,只需经一次合成,制备了性能良好的Silicalite-1膜。在60℃下原料液乙醇浓度为4.8wt.%,渗透汽化分离水中乙醇时,渗透通量为1.25kg·m^-2·h^-1,分离系数为36.2。水硅比高的合成液在二段合成温度较低的情况下,经二次合成后,60℃下原料液乙醇浓度为4.52wt.%,渗透通量和分离系数分别达2.80kg·m^-2·h^-1和34.3。采用杂原子改性,利用水热法,首次在氧化铝载体上合成出了含有廉价杂原子锡（Sn）的MFI型Sn-ZSM-5沸石分子筛膜。考察了不同的成膜条件如载体种类,Si/Sn比,晶种大小对Sn-ZSM-5膜的形貌和分离性能的影响,发现载体和Si/Sn比是主要影响因素。气体渗透率表明合成的Sn-ZSM-5沸石复合膜完整、致密。在乙醇浓度为4.52wt.%的乙醇/水体系中,操作温度为60℃时,渗透汽化分离水中乙醇时,分离系数为18.7,分离选择性低于Silicalite-1沸石膜（分离系数51.1）。将制备的Sn-ZSM-5沸石膜应用于渗透汽化分离水中低浓度乙酸,其分离性能高于Silicalite-1膜。在90℃条件下,对于乙酸浓度为5wt.%的乙酸/水体系,Si/Sn比为25的陶瓷基Sn-ZSM-5沸石膜的分离系数为7.8,通量达到0.49kg·m^-2·h^-1,而同条件下,Silicalite-1膜的分离系数小于1.5。深入分析讨论了对这两体系分离性能相异的原因。考察了Sn-ZSM-5膜分离乙酸时,膜合成液中Si/Sn比,渗透汽化分离水中乙酸操作温度和进料浓度对分离系数和渗透通量的影响。在Silicalite-1膜上复合强疏水性高分子聚合物聚二甲基硅氧烷（PDMS）层,首次研制了Silicalite-1/PDMS复合膜,确定了PDMS溶液的最佳浓度为5wt.%,最适宜的PDMS有机膜层厚度介于1.5μm到2μm之间。在莫来石管上制备了通量为2.67kg·m^-2·h^-1,醇/水选择性系数为54.9的Silicalite-1/PDMS复合膜,达到了提高Silicalite-1膜分离性能的目的。更多还原

【Abstract】 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℃.更多还原