Synthesis of Imidazolium based PILs and Investigation of Their Blend Membranes for Gas Separation.

Joannis Kallitsis,Thanasis Chouliaras,Theophilos Ioannides,Aristofanis Vollas,Valadoula Deimede

doi:10.3390/membranes9120164

Joannis Kallitsis, Thanasis Chouliaras + Show 3 more

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https://doi.org/10.3390/membranes9120164

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Abstract

Polymeric (ionic liquid) (PIL) copolymers bearing cationic imidazolium pendants and polar acrylic acid groups (P(VBCImY-co-AAx)), which both favor the interaction with CO2 molecules, have been synthesized and blended with film forming, high glass transition temperature aromatic polyether-based pyridinium PILs (PILPyr). The blend membranes based on the above combination have been prepared and characterized in respect to their thermal and morphological behavior as well as to their gas separation properties. The used copolymers and blends showed a wide range of glass transition temperatures from 32 to 286 °C, while blends exhibited two phase morphology despite the presence of polar groups in the blend components that could participate in specific interactions. Finally, the membranes were studied in terms of their gas separation behavior. It revealed that blend composition, counter anion type and acrylic acid molar percentage affect the gas separation properties. In particular, PILPyr-TFSI/P(VBCImTFSI-co-AA20) blend with 80/20 composition shows CO2 permeability of 7.00 Barrer and quite high selectivity of 103 for the CO2/CH4 gas pair. Even higher CO2/CH4. selectivity of 154 was achieved for PILPyr-BF4/P(VBCImBF4-co-AA10) blend with composition 70/30.

Highlights

Gas separation membranes are extensively applied in natural gas purification, CO2 capture, hydrogen recovery, and oxygen and nitrogen enrichment [1,2]
We have focused on the above mentioned aromatic polyethers due to their superior solubility combined with high glass transition temperatures and a series of N-methyl imidazolium containing poly(vinyl benzyl chloride-co-acrylic acid) backbone PILs that were chosen and synthesized as the second component of blend materials
PIL copolymers bearing cationic imidazolium pendants and polar acrylic acid groups, which both favor the interaction with CO2 molecules, have been synthesized in order to be used as blend constituents

Summary

Introduction

Gas separation membranes are extensively applied in natural gas purification, CO2 capture, hydrogen recovery, and oxygen and nitrogen enrichment [1,2]. Polymeric (ionic liquids) (PILs) have recently attracted considerable attention as CO2 separation membranes because they combine the inherent properties of polymers (e.g. processability, robustness) with the unique properties of ILs such as high CO2 sorption capacity, tunable physicochemical properties, and high thermal stability [3,4,5]. The majority of the PILs based on imidazolium, pyrrolidinium, or ammonium have been synthesized via free radical polymerization and show high CO2 permeability but low operation temperature and poor mechanical stability [6,7,8,9]. In order to overcome these obstacles and further increase the operation temperature, improve the separation properties and broaden their application range, the combination of a polymeric ionic liquid with a high glass transition temperature (Tg ) polymer seems to be an ideal solution [10,11,12].

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