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, composites prepared from polymer and inorganic fillers called mixed matrix membranes (MMMs) have been investigated for enhancing gas separation performance.  The low interfacial interaction between the polymer matrix and the inorganic particles is one of the problems encountered in the fabrication of good MMMs.  Interface defects can significantly reduce the gas separation performance of MMMs.  This study focused on the effects of zeolite in polyimide (PI)/zeolite composite membranes containing ionic liquids (ILs) for preventing interface defects.  The physical, thermal, and gas permeation properties of the membranes were investigated in terms of zeolite presence and IL content.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).  Free-standing composite membranes consisting of 6FDA-TeMPD PI, 66 wt% IL (1-butyl-3-methyl-imidazolium bis(trifluoromethyl-sulfonyl) imide ([C4mim][Tf2N])), and zeolite (ZSM-5) were prepared using the casting method.The IL content in the composite membrane determined by TGA measurement mostly corresponded to the feed content.  No chemical reaction occurred among the PI, zeolite, and IL in the composite membranes, as confirmed by the similarity of the 1H- and 13C-NMR results.  The SEM images show that the interfacial voids between PI and ZSM-5 decreased with increasing IL content.  The gas permeability of the PI+ZSM-5 membrane was higher than that of PI, but the gas selectivity was significantly reduced, suggesting that these results can be attributed to the interface defects.  The CO2 selectivity of the PI+ZSM-5+IL membranes was higher than that of the PI+ZSM-5 membranes because of the suppression of the interface defects brought about by the introduction of IL.

Preparation and gas permeation properties of polyimide/zeolite composite membranes containing ionic liquid

248th National Meeting (2014)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.