聚砜中空纤维载体上NaA型分子筛膜的制备

发布时间：2018-06-26 13:33

本文选题：NaA型分子筛膜 + 聚砜载体　；参考：《大连理工大学》2015年硕士论文

【摘要】：作为膜分离的一个重要分支,渗透汽化受到了许多学者的研究关注。中空纤维式膜组件与其他形式的膜组件相比,具有成本低、填充率高、有自支撑作用而占地面积小等优点。目前受到广泛关注的中空纤维渗透汽化膜材料主要是聚合物材料,但其存在溶胀、热稳定性差、渗透通量低和分离因子小等问题。而常见的无机材料,如分子筛,需要制备在成本较高的支撑体上,且还存在制成的膜组件体积较大、填充率低的问题。因此,在有机中空纤维上合成分子筛膜,对于解决上述问题具有一定的实际意义。然而,有机载体与分子筛之间结合性差,分子筛容易从载体上脱落。如何实现在有机中空纤维载体制备无机分子筛膜,使制备的膜材料兼具聚合物和无机分子筛的性能,成为渗透汽化膜领域一个重要的研究内容。本文提出以聚砜(PSf)中空纤维为支撑体,通过在有机中空纤维表面涂覆中间层,采用水热合成法在其表面合成NaA型分子筛膜,实现分子筛膜在有机中空纤维载体表面的连续致密生长。首先,采用具有亲水性PVA作为制备中间层的材料,成功在中空纤维表面制备了NaA型分子筛膜。考察了添加中间层与否、合成时间、晶种粒径、涂晶次数对分子筛膜分离性能的影响,优化了制膜的工艺。结果表明,PVA中间层的存在有利于在PSf中空纤维载体上合成连续致密,无明显缺陷的NaA分子筛膜。该膜的分离性能在合成时间大于6 h、晶种平均粒径90 nm、涂晶次数为3次时达到最佳,所制备的NaA型分子筛膜分离因子可达37.28,通量为3.53 kg·m-2·h-1。为了进一步优化膜的制备过程,减少涂晶步骤对制备工艺的影响,采用聚合物/NaA作为复合中间层,在中空纤维表面合成分子筛膜。考察了中间层材料、合成时间、涂膜方式、膜液晶种含量对分子筛膜分离性能的影响。结果表明,采用乙基纤维素(EC)/NaA复合中间层涂敷在中空纤维表面合成的分子筛膜,分离性能要高于采用PVA中间层涂敷在中空纤维表面合成的分子筛膜。涂膜方式对分子筛膜的分离性能影响很大,采用4wt%EC-50wt%NaA的复合晶种膜液一次浸涂,1.5wt%EC-xwt%NaA含量(xwt%为二次浸涂液中NaA含量)的复合晶种膜液二次浸涂的方法所制备的复合中间层较好,最佳的二次浸涂液NaA含量为80wt%,最佳合成时间大于6h,所制备的NaA型分子筛膜分离因子可达62.19,通量达到2.07kg·m-2·h-1。
[Abstract]:As an important branch of membrane separation, pervaporation has been studied by many scholars. Compared with other kinds of membrane assembly, hollow fiber membrane assembly has the advantages of low cost, high filling rate, self-supporting effect and small area. At present, the hollow fiber pervaporation membrane materials are mainly polymer materials, but there are many problems such as swelling, poor thermal stability, low permeation flux and small separation factor. The common inorganic materials, such as molecular sieve, need to be prepared on the high cost support, and there are many problems such as large volume of membrane assembly and low filling rate. Therefore, the synthesis of molecular sieve membrane on organic hollow fiber has certain practical significance for solving the above problems. However, the binding between the organic support and the molecular sieve is poor, and the molecular sieve is easy to fall off from the support. How to prepare inorganic molecular sieve membrane on organic hollow fiber carrier and make the membrane material have the properties of both polymer and inorganic molecular sieve has become an important research content in the field of pervaporation membrane. In this paper, using polysulfone (PSF) hollow fiber as support, NAA molecular sieve membrane was synthesized on the surface of polysulfone (PSF) hollow fiber by coating the intermediate layer on the surface of organic hollow fiber by hydrothermal synthesis. The continuous dense growth of molecular sieve membrane on the surface of organic hollow fiber carrier was realized. Firstly, NAA molecular sieve membrane was successfully prepared on hollow fiber surface by using hydrophilic PVA as intermediate layer. The effects of adding intermediate layer, synthesizing time, seed size and coating times on the separation performance of molecular sieve membrane were investigated, and the process of membrane preparation was optimized. The results show that the presence of PVA intermediate layer is beneficial to the synthesis of continuous dense NAA molecular sieve membrane without obvious defects on PSF hollow fiber carrier. When the synthesis time is more than 6 h, the average grain size is 90 nm, and the coating times are 3 times, the separation factor of NAA zeolite membrane is 37.28 and the flux is 3.53 kg m-2 -1. In order to further optimize the preparation process of the membrane and reduce the effect of coating on the preparation process, molecular sieve membrane was synthesized on the surface of hollow fiber using polymer / NAA as the composite intermediate layer. The effects of interlayer material, synthesis time, coating method and liquid crystal content on the separation performance of molecular sieve membrane were investigated. The results show that the separation performance of the composite interlayer coated with ethylcellulose (EC) / NAA on the surface of hollow fiber is higher than that on the surface of hollow fiber. The coating method has a great influence on the separation performance of molecular sieve membrane. The composite interlayer is better prepared by the method of 4wt-50wtNaA composite seed membrane solution once impregnated and 1.5wt-xwtNaA content (xwt% is the NaA content in the secondary impregnation solution). The optimum NaA content of secondary leaching solution is 80 wt.The optimum synthesis time is more than 6 h. The membrane separation factor of NAA molecular sieve can reach 62.19, and the flux can reach 2.07kg m-2 mh-1.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ051.893

【共引文献】