聚酰亚胺膜在稀有气体分离中的性能研究

Noble gases separation performance of polyimide membranes

稀有气体通常利用沸点的差异进行深冷分离,相对于这种传统方法,膜技术具有高效、低耗和环保等优异性能.在膜技术中,膜材料的选择及其后处理是影响气体分离效果的重要因素.选择两种不同聚酰亚胺,PI-1(BTDA-MDA/TDA)和PI-2(PMDA/BTDA-TDA),研究了其单体结构对于稀有气体分离性能的影响.在此基础上选择性能较为优异的PI-2膜进行不同条件的热处理,研究热处理温度对其气体分离性能的影响.研究发现,通过改变聚酰亚胺的共聚组成,可以调节分离膜的气体选择性与渗透性.热处理会改变膜内分子链堆积、部分膜结构的生成或消失以及去除残余溶剂的塑化作用,进而改变膜的渗透分离性能.通过控制热处理条件,可以使膜的渗透性与选择性同时提升,He渗透系数增加至19.1 Barrer,He/CH_(4)选择性提高了54%,O2/Xe选择性提升99%.

Cryogenic distillation is carried out by using the difference in the boiling points of gases to separate noble gases.Compared with this traditional method,membrane technology has excellent properties such as higher efficiency,lower consumption,and being more environmentally friendly.The selection of membrane materials and their post-treatment are critical to the gas separation efficiency of membrane technology.In this paper,the polyimides PI-1(BTDA-MDA/TDA)and PI-2(PMDA/BTDA-TDA)were selected to study the effect of their distinct structures on the separation performance of noble gases.After that,the polyimide membrane with excellent performance was heat treated under different conditions,and the influence of heat treatment temperature on gas separation performance was investigated.According to the research,by changing the composition of the polyimide,the noble gas selectivity and permeability of this polyimide membrane could be adjusted.Different heat treatment conditions could change the permeability and separation performance of the membrane by changing the chain accumulation in the membrane,forming part of the membrane structure,and removing the plasticizing effect of the residual solvent.By controlling the heat treatment conditions,the permeability and selectivity of the membrane can be improved at the same time.The He permeability coefficient increased to 19.1 Barrer,and the selectivity of He/CH_(4)increased by 54%,while the selectivity of O2/Xe increased by 99%.