不对称炭膜的制备及结构性能研究

Preparation and gas separation performance of the asymmetric carbon membrane

以Kapton型聚酰胺酸(PAA)为前体,以N,N-二甲基乙酰胺(DMAc)为溶剂和凝胶浴添加剂,分别以水、乙醇、正丙醇、正丁醇为凝胶介质,采用干湿相转化法制备不对称聚酰亚胺膜,经高温炭化制备不对称炭膜.探讨了相转化制膜工艺如铸膜液浓度、蒸发时间、凝胶介质及炭化温度等因素对不对称炭膜微结构和气体分离性能的影响,并采用SEM、XRD等手段对不对称炭膜的表面形态及微结构进行表征.研究表明,采用相转化的方法成功地制备了具有不对称结构的炭膜,相转化制膜工艺、炭化工艺对所制备不对称炭膜的结构及气体分离性能有较大的影响;控制适宜的铸膜液浓度、预蒸发时间有利于制备具有高通量、高分离选择性的不对称炭膜;提高炭化温度可以改变其微观结构,使炭膜的有序度和致密度增加,进而对膜的气体分离性能产生影响。SEM分析表明,所制备的不对称炭膜表面致密无缺陷,且具有明显的致密皮层和多孔支撑层结构;XRD显示,制备的不对称炭膜的微结构为乱层炭结构.

The asymmetric carbon membranes were prepared by the dry/wet phase inversion method and then carbonization using PAA as the precursor,DMAc as the solvent and additive.The effects of the preparation technology parameters of phase inversion and carbonization on the microstructure and gas separation performance of asymmetric carbon membranes were investigated by SEM,XRD and variable volume-constant pressure method.The results showed that the preparation technology parameters of phase inversion and carbonization greatly affect the microstructure and gas separation performance of asymmetric carbon membranes.Controlling the proper concentration of casting solution and pre-evaporation time is beneficial to preparing the asymmetric carbon membranes with the high gas permeation flux and high selectivity.The microstructure of carbonmembrane can be improved with the enhancement of carbonization temperature,which affects the gas separation performance of asymmetric carbon membrane.The SEM images indicate that the asymmetric carbon membrane is composed of the surface compact layer and porous support.Its surface is compact and free of defect.The microstructure of asymmetric carbon membranes is the disordered carbon structure according to XRD.