链状小分子在NaA分子筛膜内传质的分子取向研究

As the advances of material synthesis technique, a large amount of inorganic membranes were fabricated for purification and recycling of organic solvent in industries. However, the majority of the work predominately focused on the adjustments of the synthesis and operation conditions, which aimed to tailor pore size and minimize the membrane defects. Therefore, due to a lack of bottom-up understanding about the separation mechanism, the essential requirment for the selection of the purification method for the organic solvents based on their molecular structure was thus neglect, which significantly inhibited the industrial application of the membrane-based technology. In this work, the organic polymers of dopamine, polysulfone and lignin are used as a coating layer to modify the NaA membrane layer, prepared by the secondary growth method. The kinetic analysis of the linear molecules of methane, methanol, water, ethane, ethanol, propane, propanol and so on through the original and modified NaA membrane layer is combined with the mathematic theories and molecular simulations to explore the transport mechanism into the NaA zeolite pores. The results are expected to elucidate the influence of the organic layer on the orientation effect of light linear molecules due to its strong adsorption, which favors the increase in membrane selectivities and operational stabilities. The corresponding discoveries are believed to provide fundamental insights for the fabrication of zeolite-based membranes and equipment.

随着材料合成技术的发展，大量新型的无机膜材料被制备出来，用于工业溶剂回收和分离。然而当前分子筛基膜分离的研究方向，主要侧重于对材料本身性能的研究上，通过变换合成和操作条件，来达到调整孔径和消灭膜层缺陷的目的。由于人们对膜分离机理的不足，而忽视了对有机溶剂应根据其分子结构加以区别对待的要求，从而抑制了膜分离技术的工业化进程。本项目拟用二次生长法制备NaA分子筛膜，然后借用多巴胺、聚砜和木质素等有机聚合物修饰NaA分子筛膜层。通过分析甲烷、甲醇、水、乙烷、乙醇、丙烷、丙醇等链状小分子通过NaA膜和其修饰体的动力学过程，结合数学建模和分子模拟法，探讨链状小分子在NaA分子筛孔道的扩散过程，以阐明有机聚合物修饰体的吸附固位作用对链状小分子空间取向的影响，以期提高NaA分子筛对链状分子的选择性和操作稳定性，从而为分子筛基膜材料和装备设计提供理论基础。

研究流体小分子在限域孔道内传质过程的空间取向对于合理设计和应用分子筛材料具有重要的意义。本项目借助有机聚合物分子修饰NaA 分子筛膜层，利用有机涂层分子的吸附固位作用，定性改变链状分子在孔道入口处的分子取向，从而显著增强链状分子的传质阻力，突破单一条件下NaA 分子筛材料的尺寸限域效应极限，进而根本上改善NaA 分子筛膜对有机链状分子的选择性。通过实验成功的定性确定有机层对链状气体分子的吸附固位作用，论证了链状烯烃分子在不同取向条件下在膜层表面所遇到的的扩散能垒，为实验观察所得结果提供了理论支撑。与此同时，结合零长柱法（ZLC），通过数值求解脱附曲线，计算和分析链状溶剂分子在不同条件下所对应扩散系数的变化过程，成功的剖析出链状有机溶剂分子在NaA分子筛材料内扩散的变化规律，结果显示分子筛表面范德华力势能场的变化对链状分子的扩散过程具有重要影响。为总结上述规律，开发出一种通用型有限元法，其可以成功的计算出界面阻力势垒，所得到的数学模型可以作为初步计算膜间气体分离性能的重要工具。