Abstract: 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.

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