464312 Thermally-Rearranged Highly Selective Gas Separation Membranes from Hydroxyl-Functionalized Triptycene-Based Polyimide for Natural Gas Upgrading

Thursday, November 17, 2016: 1:06 PM
Plaza B (Hilton San Francisco Union Square)
Fahd I Alghunaimi, Bader Ghanem, Octavio Salinas and Ingo Pinnau, Advanced Membranes and Porous Materials Center, KAUST, Thuwal, Saudi Arabia

Recently, a new polyimide of intrinsic microporosity (TDA1-APAF) prepared from 9,10-dimethyl-2,3,6,7-triptycene tetracarboxylic dianhydride (TDA1) with commercially available 2,2-bis(3-amino-4-hydroxyphenyl) hexafluoropropane (APAF) diamine monomer exhibited excellent gas-pair selectivities for O2/N2 and CO2/CH4 but with moderately high gas permeabilities. To enhance gas permeabilities, conversion of hydroxyl-containing polyimide into polybenzoxazole was used by thermal rearrangement of the aromatic polymer chain with decarboxylation at elevated temperature. TR-TDA1-APAF membrane displayed excellent O2 permeability of 311 Barrer coupled with O2/N2 selectivity of 5.4 and CO2 permeability of 1328 Barrer coupled with a CO2/CH4 selectivity of 27. Gas mixture permeation experiments with a 1:1 CO2/CH4 feed mixture demonstrated higher mixed- than pure-gas selectivity (~33) with CO2 permeability of 1270 Barrer. Interestingly, physical aging over 180 days resulted in an enhanced O2/N2 selectivity of 6.3 with O2 permeability of 185 Barrer and CO2/CH4 selectivity of 35 coupled with CO2 permeability of 699 Barrer. These results suggest that thermally-rearranged membranes from hydroxyl-functionalized triptycene-based polyimides are promising candidate membrane materials for CO2removal from natural gas and air separation applications.

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