Application of facilitated transfer mechanisms of SEBS/[P_(14)666][TMPP] composite membrane on CH₄/N₂ separation

CH4/N-2 separation is one of the most challenging gas separation tasks and plays a significant role in the global warming hiatus. Membrane-based separation is a promising method for industrial applications but has been limited by its poor CH4/N-2 selectivity. Therefore, an ionic liquid with excellent differential binding properties to CH4 and N-2 is required for this study. [P-(14)666][TMPP] (bis (2,4,4 trimethylpentyl) phosphinate, trihexyl (tetradecyl) phosphanium) was selected from 26 ionic liquids (ILs) to prepare IL-polymer membranes (ILPMs). It led to a 57.9 % increase in CH4/N-2 selectivity of 7.31 and a 2539.9 % increase in CH4 permeability of 128.3 barrer compared with neat membrane. DFT simulations reveal that the facilitated transfer mechanism could enhance CH4/N-2 separation. This study also shows that (1) the C-H center dot center dot center dot O forms hydrogen bonding (HB); (2) the differences of CH4 and N-2 in geometry and electrostatic potential (ESP) distribution lead to different steric hindrance effects that could be the decisive factor for the outstanding performance of prepared ILPMs in this study.