(552c) PIM-1/Matrimid Hollow Fiber Membranes for Natural Gas and Air Separation

Polymers of intrinsic microporosity (PIM-1) have received worldwide attention as new polymer type for gas separation but most PIM-1 researches have been conducted on dense flat membranes. For the first time, we have fabricated PIM-1/Matrimid membranes in a useful form of hollow fibers with promising separation performance. The newly developed hollow fibers comprising 5-15 wt% of highly permeable PIM-1 not only possess much higher gas-pair selectivity than PIM-1 but also have much greater permeance than pure Matrimid fibers. Data from Positron annihilation spectroscopy (PAS), field emission scanning electron microscopy (FESEM) and apparent dense layer thickness indicate that the blend membranes have an ultrathin dense layer thickness of less than 70 nm. High flux defect-free as-spun blend membranes with gas-pair selectivity more than 90% of the intrinsic values of dense films can be spun directly from dopes containing 5 wt% PIM-1 into Matrimid while post annealing and additional silicone rubber coating are needed for membranes containing 10 and 15 wt% PIM-1. Comparing to Matrimid, the CO₂ permeance of as-spun fibers containing 5 and 10 wt% PIM increases 78% and 146%, respectively (e.g., from original 86.3 GPU to 153.4 GPU and 212.4 GPU) without compromising CO₂/CH₄ selectivity. The CO₂ permeance of the fiber containing 15 wt% PIM displays a greater improvement of 2.8 folds to 243.2 GPU with a CO₂/CH₄ selectivity of 34.3 after silicon rubber coating. Under binary gas tests of 50/50 CO₂/CH₄, this fiber shows a CO₂ permeance of 188.9 GPU and a CO₂/CH₄ selectivity of 28.8. The same fiber also has an impressive O₂ permeance of 3.5 folds higher than the pristine Matrimid (e.g., from original 16.9 GPU to 59.9 GPU) with an O₂/N₂ selectivity of 6.1. The newly developed membranes demonstrate an exceptional gas separation performance and have a great potential to be used for natural gas purification, air separation and CO₂ capture.