Gas separation performance of branched PIM-1 thin-film composite hollow fiber membranes

In this work, we explored for the first time the gas separation performance of a branched PIM-1 polymer ( 11 % substituted) in a hollow fiber-thin film composite membrane (HF–TFCM) configuration. HF-TFCMs were successfully obtained by the dip-coating methodology with a 1–2 µm thin selective layer of the branched PIM-1 (B-PIM-1). The permeability of these membranes to pure carbon dioxide, methane, nitrogen, carbon monoxide and hydrogen was tested in a tubular membrane module. The herein prepared HF-TFCMs offered a remarkable initial CO₂ permeance of 650 GPU, along with ideal gas selectivity of 20.8 and 14.8 for CO₂/N₂ and CO₂/CO separations, respectively. In addition, the aging of the B-PIM-1 HF-TFCM was weekly monitored over 307 days, showing a 54 % permeance drop for CO₂ with a 24 % drop in CO₂/N₂ selectivity, highlighting a moderate aging resistance of the B-PIM-1 structure. The membrane performance for mixed gas separation was further explored with CO₂/N₂ mixtures in the range 10–70 CO₂ vol%, and, for the first time, with a CO₂/CO mixture (50/50 vol%), showing similar performance to that observed with pure gases for CO₂/N₂ separation and only a slightly lower CO₂ permeance in CO₂/CO separation. These results emphasize the potential of B-PIM-1 hollow fibers for the recovery of CO₂ from CO₂/N₂ and CO₂/CO mixtures. In addition, gas sorption isotherms of all gases at 30 °C were obtained and modelled. The solubility results showed that the branched structure did not affect gas solubility compared to the conventional predominantly di-substituted PIM-1.