Polymer membrane-based gas separation has drawn attention because of its low cost and low energy demands. High gas permeability and selectivity, as well as membrane strength and thermal stability, are essential for gas separation membranes. In the past decades, polyimide membrane modified by amine solution have been investigated for enhancing gas separation performance(Immersion method). However, the membrane caused swelling by this immersion method. The swelling is one of the problems encountered decreasing of gas separation. This study focused on the gas permeation and separation properties of polyimide membrane modified by aromatic amine vapor. The base fluorine-containing polymer was synthesized by polycondensation using the monomers, 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) and 2,3,5,6-tetramethyl-1,4-phenylene diamine (TeMPD). The modified membrane prepared by two methods. In one modified method, membranes were modified by amine vapor from one side (method A). In another method, membranes were modified from both sides (method B). The reaction ratio of membrane were measured by ATR–FTIR and FT–IR. At the membrane surfaces, amine vapor affect stronger than amine solution at membrane surface. In contrast, amine vapor affect weaker than amine solution at membrane bulk layer. The permeability coefficient of pure gases (i.e., hydrogen (H2), oxygen (O2) nitrogen (N2), carbon dioxide (CO2), and methane (CH4)) in polyimide membranes were determined using a constant-volume / variable-pressure method. The gas permeabilities of all modified membranes depend on gas molecular size. Some of gas separation propeterties of membranes which modified by amine vapor such as H2 / CH4 was higher than that of membranes modified by amino solution. Besides, there are no differences between method A and method B. Therefore, aromatic amine vapor modification for 6FDA polyimide membranes was better than amine solution modification without exposed side.

Gas permeation and separation properties of polyimide modified by aromatic amine vapor

250th National Meeting (2015)

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