Ionic liquid tethered PEG-based polyurethane-siloxane membranes for efficient CO 2 /CH 4 separation

This study introduces a new polyethylene glycol (PEG) based polyurethane-siloxane membrane containing a quaternary ammonium ionic liquid for CO /CH separation. The designed ionic liquid was prepared in two steps: (i) (3-chloropropyl)triethoxysilane (CPS) and N,N-dimethylpropyl amine (NDPA) were reacted with each other to form the methoxysilane-functionalized quaternary ammonium component, then (ii) chloride ion (Cl ) of the product was exchanged with tetrafluoroborate ion (BF ). The resulting compound, a reactive methoxysilane-functionalized ionic liquid (Si-IL) was chemically anchored to the polymer backbone through the sol-gel hydrolysis and condensation reaction. Based on the permeation tests, the IL containing PEG-based polyurethane-siloxane membranes at different concentration of Si-IL (XSi-PPUIL) were found to be potential candidates for CO removal from CH . For instance, the CO /CH selectivity of XSi-PPUIL membranes with the Si-IL content of 10 wt% was 3.3-fold greater than the Si-IL free membranes; while, the CO permeability for IL tethered membranes was 9.7% higher than the corresponding IL-free membrane.