於成膜程序中釋放小分子對聚醯亞胺高分子薄膜之氣體分離效能之影響

The effect of evolved small molecules in membrane formation processes on the gas separation performance of polyimide membranes

吳其祐(Wu, Chi Yu)

指導教授 ： 劉英麟

國立清華大學/工學院/化學工程學系/碩士(2015年)

摘要

本研究以不同方法改質聚醯亞胺，使其於熱處理成膜程序中脫除出小分子，使其於聚醯亞胺薄膜之中生成具有選擇性的孔洞，應用於薄膜氣體分離。本研究之第一部份以2-呋喃甲胺(furfurylamine)對聚醯亞胺進行開環加成反應，所得之產物再經由熱處理程序進行閉環反應，在成膜過程中將接上之2-呋喃甲胺脫除，還原成醯亞胺基之結構。結果顯示，經此改質程序後所得到的聚醯亞胺薄膜，在正子消散光譜分析中顯示較為窄而小的自由體積分佈，因而對於氫氣的氣體透過與分離有相當的影響，氫氣的透過係數由23.1 barrer提升至26.7 barrer，氫氣/氮氣選擇比由55.0提升至72.2，而氫氣/二氧化碳之選擇比由1.8提升至2.3。本研究之第二部份以米氏酸(Meldrum’s acid)衍生物與聚醯亞胺進行摻混，在熱處理成膜程序中，米氏酸受熱分解而放出二氧化碳及丙酮，並同時進行交聯反應，與聚醯亞胺形成半互穿網型結構(semi-interpenetrating polymer networks)，結果顯示摻混20 wt%的米式酸衍生物時，聚醯亞胺薄膜的氫氣/氮氣與氫氣/二氧化碳的選擇比均提升了二至三倍，在正子消散光譜分析中也顯示較為窄而小的自由體積分佈。本研究結果顯示，在聚醯亞胺成膜程序中導入釋放小分子的機制，可以有效提高薄膜對於氫氣的氣體分離選擇性。

關鍵字

氣體分離 ； 高分子薄膜 ； 小分子釋放 ； 熱處理 ； 可逆開環反應 ； 聚醯亞胺 ； 2-呋喃甲胺 ； 米氏酸

並列摘要

Polyimides are one of the attractive materials for gas separation due to their high thermal stability and chemical tolerance. Modification of polyimides is a feasible approach to enhance the separation performance of polyimides. In this work, the effect of small molecule releases in membrane formation processes on the gas separation performance of polyimide membranes has been investigated. First, a reversible ring-opening reaction of polyimide membrane with furfurylamine (FFA) is carried out by means of thermal processes. Portion of the polyimide chain undergoes the amidation reaction with the amine groups of FFA to form the product of PIFFA. Upon heat, the sample process a reimidization reaction with release of FFA molecules and result in the sample of PIFFA250. Gas separation experiments results shows the PIFFA film declines only slightly in gas permeation, but maintains the efficiency in gas separation. The PIFFA250 film, which is obtained by 250 oC heat treatment to PIFFA film, shows increases in hydrogen gas (H2) permeability and selectivity for a certain extent. Compared with the original polyimide films, the permeability of H2 increased from 23.1 to 26.7 barrer, and the H2/N2 and H2/CO2 selectivity increased from 55.2 to 71.6 and 1.8 to 2.3, respectively. The second part of this study employs Meldrum’s acid (MA) derivatives as modifiers for PIs. Under heat treatment, MA groups decompose accompanied with releases of acetone and carbon dioxide. The thermally-treated MA-modified polyimide membranes render better permselectivity results of H2. Compared with original polyimide films, the H2/N2 and H2/CO2 selectivity of the modified PI (possessing 20 wt% MA derivative compounds) increase by two or three times. The gas separation properties of the modified PIs has been correlated to the changes in the free volumes caused by the releases of small molecules in the membrane formation processes at high temperatures.

並列關鍵字

gas separation ； polymeric membrane ； release of small molecule ； heat treatment ； reversible ring-opening reaction ； polyimide ； furfurylamine ； Meldrum's acid

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