【作者】 马静；

【导师】 张敏华； 姜忠义；

【作者基本信息】 天津大学 ， 化学工艺， 2010， 博士

【摘要】 工业应用中的渗透蒸发膜多数为复合膜,其结构稳定性直接关系到膜的使用寿命。研究高分离性能、高稳定性的复合膜有重要理论意义和应用价值。本研究以乙醇和水的渗透蒸发分离为研究对象,以增强复合膜分离层与支撑层界面相互作用、提高复合膜结构稳定性为出发点,受生物粘合现象的启发,将生物粘合剂引入复合膜中,提出了一种制备复合膜的新方法。基于生物粘合机理,对复合膜的界面相互作用进行分析和调控,获得了具有高稳定性和高分离性能的复合膜。首先,在壳聚糖(CS)分离层和聚丙烯腈(PAN)支撑层间引入了一层卡波姆(CP)生物粘合剂作为过渡层,制备了GCCS/CP/PAN三层结构的复合膜。T-型剥离测试证实了CP的引入增强了CS/PAN间的界面粘合强度。接触角测试结果表明了CP可改善PAN支撑层的亲水性,增强与CS分离层的界面相容性。渗透蒸发实验结果表明CP的引入可提高膜的分离选择性。在此基础上,将明胶(GE)、透明质酸(HA)生物粘合剂引入复合膜中,制备了GCGE/PAN、GCHA/HM-PAN两层结构复合膜。GE、HA生物粘合剂既能与支撑层形成牢固的粘合又具有良好成膜性和强亲水性,可直接用作复合膜的分离层。对比所考察的三种复合膜的渗透蒸发性能,GCHA/HM-PAN复合膜的脱水性能最高:当HA浓度为0.8 wt.%,交联度为0.3及采用水解改性的PAN为支撑层时,GC(0.3)HA(0.8)/HM-PAN膜的渗透通量为1.634 kg/(m2h),分离因子为233。尝试了采用分子动力学模拟技术从分子水平上揭示膜材料-膜微观结构-膜分离性能的关系,初步探究了三种复合膜的界面粘合机理。界面粘合键均由氢键、范德华力和静电力非键相互作用组成。在不同复合膜界面处占主导的作用力不同:CS/CP/PAN为静电力;GE/PAN为范德华力;而HA/HM-PAN为氢键。其中,HA/HM-PAN结构的界面相互作用最强,从而可以抑制分离层高分子链的运动性和溶胀,获得高分离选择性。考察了GCCS/CP/PAN、GCGE/PAN、GCHA/HM-PAN复合膜对乳酸与乙醇酯化反应平衡移动的影响。渗透蒸发与酯化反应的耦合,可及时将生成的水移出,打破原有化学平衡限制,使乳酸乙酯产率提高了28.2%。确定了适宜的耦合工艺参数,使得乳酸乙酯产率反应8 h时高达94.9%。更多还原

【Abstract】 Most pervaporation members for industrial use were composite membranes, and the structural stability of the composite membrane was closely related to the service life. It is very important both in theory and practicality to develop the composite with high structural stability and separation performance. In the present work, the pervaporation separation of the water and ethanol mixture was chosen as the investigation object and the goals were to increase the interfacial interaction between the separation layer and the support layer, and enhance the structural stability of composite membrane. Inspired by the bioadhesion phenomena, a new method of fabricating composite membrane was found by introducing bioadhesives into it. Furthermore, the interfacial interaction was analyzed and adjusted basing on the bioadhesion principle, and the composite membranes with high structural stability and separation performance were fabricated.Firstly, the GCCS/CP/PAN composite membrane with three layers structure was fabricated by introducing CP bioadhesive as the intermediate layer. T-peel test veri?ed the interfacial adhesion strength of CS/PAN membrane was considerably increased by the introduction of CP. Contact angle measurement results suggested that CP was helpful to enhance the hydrophilic nature of PAN support layer and resulted in a better compatibility with CS separation layer. With the presence of the CP intermediate layer, the separation selectivity of CS/PAN membrane was greatly increased. Basing on this, GCGE/PAN and GCHA/HM-PAN composite membranes with two layers structure were fabricated. GE and HA bioadhesives could firmly adhere onto the support layers and displayed extremely high hydrophilicity, which acted as the separation layer of composite membrane directly. Comparing the pervaporation performance of GCCS/CP/PAN, GCGE/PAN and GCHA/HM-PAN membranes, the GCHA/HM-PAN membrane showed the best separation efficiency. Using the hydrophilically modified-PAN (HM-PAN) as the support layer, when the HA concentration was 0.8 wt.%, and the cross-linking degree was 0.3, the GA(0.3)HA(0.8)/HM-PAN membrane displayed the permeation flux of 1.634 kg/(m2 h) and the separation factor of 233 for 90 wt.% aqueous ethanol solution at 353 K with a flow rate of 60 L/h. Secondly, molecular dynamics simulation was employed to reveal the relationship of membrane materials, microstructure and separation performance from molecular level, and explored the interfacial adhesion principle of CS/CP/PAN, GE/PAN and HA/HM-PAN composite membranes. Interfacial energies were composed of hydrogen bond, van der Waals force and electrostatic force, and the dominant forces at the interfaces of three kinds of composite membranes were different. Electrostatic force, van der Waals force and hydrogen bond played a dominant role at the interface of CS/CP/PAN, GE/PAN and HA/HM-PAN composite membranes, respectively. Meanwhile, the HA/HM-PAN membrane showed the strongest interfacial interaction, which could further inhibit the polymer chains mobility and decrease the swelling of the separation layer, leading to an improved selectivity.Finally, the effects of GCCS/CP/PAN, GCGE/PAN and GCHA/HM-PAN composite membranes on the chemical balance motion of esterification between lactic acid and ethanol were investigated. Pervaporation-assisted esteri?cation results suggested that the incorporation of pervaporation process to preferentially remove water from the reaction mixture, broke the limit of initial chemical balance, and the yield of ethyl lactate was substantially enhanced by 28.2%. Furthermore, the optimum thchnological parameter for coupling process was confirmed, and the yield of ethyl lactate reached to 94.9% after 8 h.更多还原