Abstract:

In order to recover C₃H₆ from off-streams of polypropylene plants, PDA@PEBA2533 membranes with stronger affinity for C₃H₆ were prepared by depositing polydopamine (PDA) layers on the surface of poly(ether-block-amide) copolymer (PEBA2533) membranes using the dip-spin method invented by our group. The synthesized PDA particles and membranes were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The effect of PDA deposition time on the membrane morphology, structure and separation performance was investigated, as well as the effect of operating conditions such as temperature and pressure on the membrane separation performance. The separation effect of C₃H₆/N₂ mixture with different C₃H₆ concentration on PDA@PEBA2533 membrane and the long-time separation stability of the membrane were explored. The results showed that the deposition of PDA on the surface of PEBA2533 membranes effectively improved the separation performance of the membranes. When the deposition time was not less than 24h, a continuous PDA layer was formed. With the increase of deposition time, the membrane layer gradually thickened, the gas permeance first increased and then decreased, and the selectivity continued to rise. The membrane with 24h of deposition time indicated the best separation performance among the membranes prepared. Increasing the operating temperature and pressure, the permeance of both C₃H₆ and N₂ increased, while the C₃H₆/N₂ selectivity decreased. Increasing the concentration of C₃H₆ in the gas mixture, the permeance and selectivity of PDA@PEBA2533 membrane for C₃H₆ increased and then decreased. On the PDA@PEBA2533 membrane showing the best separation performance, the C₃H₆ permeance increased from 8.25GPU to 71.42GPU and the C₃H₆/N₂ selectivity decreased from 22.92 to 10.14 for a gas mixture with 20% of C₃H₆ when the temperature was increased from 0℃ to 50℃ at 0.2MPa. The membrane was stable for C₃H₆/N₂ separation during a 130h experiment. The membrane as synthesized had advantages over other membranes for separating C₃H₆/N₂ mixtures.

Key words: C₃H₆/N₂ mixture, separation, dip-spin method, PDA@PEBA2533, membrane

摘要：

为回收聚丙烯制备尾气中的丙烯，采用本实验室独创的浸渍-旋转法在聚醚嵌段共聚酰胺（PEBA2533）膜表面沉积聚多巴胺（PDA）膜层制备出对C₃H₆具有更强亲和性的PDA@PEBA2533膜。利用扫描电子显微镜（SEM）和X射线衍射（XRD）对PDA颗粒和膜进行表征。考察了PDA沉积时间对膜形貌、结构以及分离性能的影响，也考察了温度和压力等操作条件对膜分离性能的影响。探索了PDA@PEBA2533膜对不同C₃H₆浓度的C₃H₆/N₂混合气的分离效果以及膜的长时间分离稳定性。结果表明，沉积PDA于PEBA2533膜表面有效提高了膜的分离性能。当沉积时间不小于24h时，可得到连续的PDA膜层，随沉积时间的增加，膜层逐渐增厚，气体渗透速率先增大后减小，选择性持续上升，沉积24h所制备的膜分离性能最佳。增大操作温度和压力，膜对C₃H₆和N₂的渗透速率均增大，C₃H₆/N₂选择性则降低。增大混合气中C₃H₆浓度，膜对C₃H₆的渗透速率和选择性均呈现先上升后下降的趋势。在所制备的分离性能最好的PDA@PEBA2533膜上，0.2MPa时，对C₃H₆体积分数为20%的混合气，温度从0℃提高到50℃，C₃H₆渗透速率从8.25GPU增加到71.42GPU，C₃H₆/N₂选择性从22.92降低至10.14。在130h的气体分离实验中，该膜表现出良好的稳定性。该膜与其他分离C₃H₆/N₂混合气膜相比具有一定的优势。

关键词: C₃H₆/N₂混合气, 分离, 浸渍-旋转法, 聚多巴胺@聚醚嵌段共聚酰胺, 膜