Abstract
Poly(1-trimethylsilyl-1-propyne) (PTMSP) is a high free volume polymer with exceptionally high gas permeation rate but the serious aging problem and low selectivity have limited its application as CO2 separation membrane material. Incorporating inorganic nanoparticles in polymeric membranes has been a common approach to improve the separation performance of membranes, which has also been used in PTMSP based membrane but mostly with respect to tackling the aging issues. Aiming at increasing the CO2 selectivity, in this work, hybrid membranes containing four types of selected nanofillers (from 0 to 3D) were fabricated using PTMSP as the polymer matrix. The effects of the various types of nanofillers on the CO2 separation performance of the resultant membranes were systematically investigated in humid conditions. The thermal, chemical and morphologic properties of the hybrid membranes were characterized using TGA, FTIR and SEM. The gas permeation properties of the hybrid membranes were evaluated using mixed gas permeation test with the presence of water vapour to simulate the flue gas conditions. Experiments show that the addition of different fillers results in significantly different separation performances; The addition of ZIF-L porous 2D filler improves the CO2/N2 selectivity at the expenses of CO2 permeability, while the addition of TiO2, ZIF-7 and ZIF-8 increases the CO2 permeability but the CO2/N2 selectivity decreases.
Highlights
Since the late 1960s, membrane-based separation processes have gradually been recognized as feasible alternatives to conventional purification and separation processes [1]
We found that Zeolitic imidazolate frameworks (ZIFs)-7 had relatively better dispersion property in chloroform while ZIF-8, ZIF-L and TiO2 could be dispersed better in cyclohexane, both solvents were employed in fabrication of hybrid membrane
We investigated the effect of ZIF-L loadings in PTMSP membrane by preparing samples containing three different ZIF-L loadings (5 wt %, 10 wt % and 20 wt %)
Summary
Since the late 1960s, membrane-based separation processes have gradually been recognized as feasible alternatives to conventional purification and separation processes [1]. Due to the non-ideal interface between the additives and the polymer phase, adding nanofillers into polymeric matrix of a membrane will result in significant improvement in gas permeability but relatively moderate enhancement in gas selectivity [10]. ZIF-8 into polymeric membranes could improve the gas permeability and enhance selectivity [20,21,22]. Non-porous nanofillers have been reported to be able to significantly change gas separation performances, typically due to specific affinity with a target molecule (transport via selective surface diffusion phenomena) or interactions with polymeric chain packing, leading to higher free volume within the polymer matrix [31]. Various non-porous additives has been used to fabricate hybrid membranes for gas separation purpose, such as TiO2 , fumed silica and other metal oxides [5]. The separation performance data are analyzed and the influence of the various fillers on the gas transport mechanism through the hybrid membranes is discussed
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