【作者】 巫树锋；

【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】 有序介孔分子筛膜因其独特的结构优势,及其在许多跨学科领域中巨大的应用潜力,正成为材料科学家们研究的热点。介孔膜是指孔径在2～50 nm之间的多孔膜,它不仅具有无机材料良好的化学稳定性、机械强度、耐热性、抗菌性、无毒等优点,还具有普通无机膜所不具备的特殊尺寸效应、功能性等优点。有序介孔膜范畴中具有三维孔道结构的薄膜材料由于其三维可通的孔道结构,有利于物料的扩散与传输而更具应用潜力。由三维介孔MCM-48分子筛所形成的支撑膜,更以其均一的孔径分布和较大的孔道结构在膜反应器、超滤分离、传感器和微电子绝缘层等方面的应用有着巨大的潜在优势。然而,MCM-48膜的制备条件比较苛刻且水热稳定性较差,因此有关MCM-48膜制备及生长机理的研究很少,还有许多问题亟待解决。开展MCM-48膜分子筛膜的制备及膜层改性处理增强其水热稳定性和MCM-48膜应用的研究具有重要的意义。本文采用多种处理方法对MCM-48膜的合成工艺及机理进行了深入系统的研究,并对MCM-48膜进行烷基化处理增强膜的水热稳定性和疏水性,然后利用烷基化MCM-48膜对乙酸乙酯（EA）和水混合物的分离效果与机理进行研究。利用烷基化MCM-48膜与固定化木瓜蛋白酶组装成填充式的酶膜反应器,研究酶催化反应的连续性和MCM-48膜的分离性能。本研究所得到的具体成果如下:1、在孔径约1μmα-Al₂O₃载体上通过优化合成次数原位制备了较为完整的MCM-48膜,膜对N₂的渗透通量约为3.2×10^-7 mol/（m².s.Pa）,且H₂/N₂分离因数可达2.95。经考察发现膜的完整性主要由载体的孔径尺寸、膜的合成次数等因素决定。膜层内部应力随着合成次数的增加也逐渐累积,多于三次的合成MCM-48膜开始出现裂纹,导致膜性能不再继续转好;同时在膜组装界面处,除了存在无机前躯体与模板剂的自组装过程,也存在原膜层在碱性溶胶中的部分解聚,导致膜厚不随合成次数增多而增加。2、利用硅溶胶浸渍法对两种不同孔径（A类,3-5μm;B类,～1μm）的α-Al₂O₃载体进行预处理,改善载体的表面状况。经研究发现硅溶胶浸渍法能有效阻止合成溶胶向载体内部渗透,且利于MCM-48膜与载体以Si-O-Si键牢固结合。但是在焙烧过程中由于干硅胶和MCM-48膜的应力释放而产生较多裂纹,导致在膜对N₂的总渗透通量中努森扩散只占到70%（A）和85.7%（B）。然后利用涂覆过渡层法在B类载体表面涂覆一层SiO₂,并发现SiO₂层可以在阻止合成溶胶渗透的同时,在载体表面形成裂缝较少的MCM-48膜,其对N₂的渗透通量为4.52×10^-7mol/（m².s.Pa）,H₂/N₂分离因数和努森扩散率分别为3.1和87%。3、利用提拉法在B类载体表面涂覆介孔品种,经研究发现介孔晶种层可以诱导完整的MCM-48膜在载体表面生长,但由于晶种层不足够致密而容易导致部分合成溶胶向载体内部渗透。而真空涂敷晶种层法可以避免这个问题,借助压差驱动力将晶种均匀牢固地镶嵌在载体表面孔口。此法既可以有效地收缩载体表面孔径,又可以阻挡合成溶胶的渗透。在此载体上经过三次水热合成就可以制备出对N₂不透的完整MCM-48膜。经过焙烧,膜对N₂的渗透通量为1.91×10^-7mol/（m².s.Pa）,H₂/N₂分离因数和努森扩散率分别可高达3.33和97.8%。4、利用不同烷基链长的硅烷偶联剂对MCM-48膜进行烷基化,考察了烷基化对膜水热稳定性的影响,并将烷基化后的MCM-48膜应用到EA/H₂O混合物体系的分离,发现烷基化MCM-48膜对含EA wt5%的EA/H₂O体系有比较好的分离浓缩效应。应用C₈H₁₇-MCM-48膜在室温下分离此体系可以得到的分离因数高达71,总通量为1.5kg/（m².h）。换用链长较短的C₃H₇-MCM-48膜或CH₃-MCM-48膜虽然可以得到更大的总渗透通量,但是分离因数却有所降低,分别为62和36。疏水膜由嫁接的烷基链和吸附在之上的EA分子组成,膜层对疏水性的EA分子选择性的吸附,进而产生分离效能。5、将固定化木瓜蛋白酶封闭在介孔MCM-48膜管式分离器的壳程组装成填充式酶膜反应器,建立连续酶解酪蛋白的催化模型。结果表明:烷基化MCM-48膜能有效地阻止较大酶分子和蛋白质分子渗透,同时可以使小分子的水和反应产物酪氨酸分子透过而初步实现产物的分离。随着连续反应时间的延长,酪蛋白的降解量和分离样品在275nm处的特征吸收都经历从急速下降到相对稳定的过程。当进料量为5ml/min和10ml/min且连续反应5h时,酪蛋白的降解量和渗透液的吸光度分别相对稳定在24.6%和0.35,18.4%和0.26。更多还原

【Abstract】 The ordered mesostructured membranes are becoming research focus in chemistry field, owing to their superior properties and great potential applications in many scientific fields. Mesoporous membranes with pore size of 2-50 nm not only have excellent properties, such as thermal and chemical stability, mechanical strength, antibacterial and so on, that inorganic membranes possess but have regular arrays of uniform channels and the dimensions. Among the mesoporous membranes, the type which possess 3D pore structures have more and more attentions for the good transportation. And the MCM-48 membrane with 3D pore structure is a promising material for membrane-based separation processes, catalysts, and chemical sensors, etc.However, it is difficult to prepare a compact MCM-48 membrane which has good hydrothermal stability, so the researches on theoretical foundation of the formation of MCM-48 membrane are very few, many problems are urgently to be solved. Study on the preparation, modification and application of MCM-48 membrane will have a theoretical and practical significance. In this works, the preparation and mechanism of the compact mesoporous MCM-48 membrane on the porousα-Al₂O₃ tube were studied in detail. The MCM-48 membranes were also silylated to enhance the hydrothermal stability and hydrophobic property, which were suitable for the separation of EA/H₂O system. Besides this, the immobilized enzyme membrane reactor was installed by the immobilized papain and the silylated MCM-48 membrane, which could separate the products as the reaction was continuous. This thesis mainly includes several aspects:1. The MCM-48 membranes were in-suit prepared on the supports with pore size of about 1μm with optimized synthesis. The membranes had the permeation for N₂ of 3.2×10^-7 mol/（m².s.Pa） and the H₂/N₂ separation factor of 2.95. The results showed that the factors including the large pore size of the supports and the times of hydrothermal synthesis played an important role in the compactness of membrane. The stress in the membrane was increased with increasing the times of synthesis at the presence of large pore size. With more than three time’s synthesis the membrane tended to be crack. At the same time, in the high alkaline sol, there present not only the self-assembly of the inorganic precursor and the surfactant, but also the partly depolymerization of the in-suit membrane. As a result, the membrane could not grow much thicker and thicker with increasing the times of synthesis. 2. The MCM-48 membranes were formed on the porous supports （A, 3-5μm; B,～1μm） which were prefilled by silica sol. The silica sol could reduce the pore size of the supports to prevent the penetration of the synthesis sol and favor for the growing of the MCM-48 membrane on surface by the bond of Si-O-Si. But because of the exiting of much stress contained in the dry silicon gel, the membrane would be much crack in the process of calcinations. As a result, the Knudsen contribution to the total flux for N₂ was about 70% and 85% for A and B tube, respectively. Basing on the good effect of the prefilled methods, a silica transition was made on the surface of B tube. The results showed that the transition layer not only prevented the penetration of the synthesis sol, but also favored for the formation of more compact membrane with little crack. The membrane had the permeation for N₂ of 4.52×10^-7 mol/（m².s.Pa）, and relative high H₂/N₂ separation factor and Knudsen contribution （K%）, 3.1 and 87%, respectively.3. More compact MCM-48 membrane was prepared on the B supports with dip-coating seeds layer. The mesoporous seeds had a good effect on inducing the growing of membrane on the supports. But the dip-coating seeds layer was not tight for synthesis sol and resulted to the penetration into the supports. Fortunately, the problem could be resolved by the vacuumed coating methods. The MCM-48 particles with appropriate size could stuff the mouths of the surface pores strongly by pressure-driven. Then a thin and compact mesoporous MCM-48 membrane impermeable for N₂ had been successfully synthesized on B supports with optimized synthesis. After calcinations, the MCM-48 membrane had the the permeation for N₂ of 1.91×10^-7 mol/（m².s.Pa）, and the relative high H₂/N₂ separation factor and the Knudsen contribution （K%）, 3.1 and 87%, respectively.4. The MCM-48 membranes were silylated by silane coupling agent with different alkyl chain. The effect on the hydrothermal stability of MCM-48 membrane was investigated. And the silylated MCM-48 membrane was successfully applied in the separation of EA/H₂O mixture. The results showed that the silylated MCM-48 membrane had a good effect on the separation of EA/H₂O system with EA concentration of 5% （w/w）. The C₈H₁₇-MCM-48 membrane had a relative high separation factor for EA/H₂O and large total flux, 71 and 1.5 kg/（m².h）, respectively. Although the C₃H₇-MCM-48 and CH₃-MCM-48 membranes had the larger total flux, the separation factor was decreased to 62 and 36, respectively. The hydrophobic membrane was formed by the interconnection of the alkyl group and the adsorpted EA molecules. The EA molecules could penetrate the membrane selectively following the adsorption-diffusion mechanism.5. The immobilized enzyme membrane reactor was prepared by enclosing the immobilized papain in the shell pass of tubular MCM-48 membrane separator. The little molecules, such as H₂O and tyrosine, could penetrated through the silylated MCM-48 membrane, while the larger molecules could be rejected in the shell pass. As the reaction time went on, both the degradation rate of casein and the absorbance at 275nm of penetration liquid underwent a process from dramatic decline to relatively stable period. When the reaction was continuous for 5hours, the degradation rate and the absorbance of penetration liquid were 24.6% and 0.35, 18.4% and 0.26, respectively for the feed back 5ml/min and 10ml/min.更多还原