“Reverse permselectivity” of N₂ over CH₄ in aromatic polyimides

High‐Performance Membranes from Polyimides with Intrinsic Microporosity

“…[23] In contrast, for the majority of glassy polymers He > CO 2 , and for most aromatic polyimides N 2 > CH 4 . [38,39] For each gas, permeabilities increase in the sequence PIM-PI-3 < PIM-PI-1 < PIM-PI-8, consistent with evidence from nitrogen sorption studies as described above. The gas permeabilities obtained for PIM-PI-8 are by far the highest ever reported for a polyimide (compare, e.g., P O 2 ¼ 213; P CO 2 ¼ 1400 Barrer).…”

“…It is noteworthy that the PIM-polyimides, like PIM-1, appear to show a preference for CH 4 over N 2 , whereas the vast majority of polyimides show reversed selectivity of N 2 over CH 4 . [38,39] A route to a new range of high-free-volume polyimides has been demonstrated. The combination of high permeability and good selectivity, along with excellent thermal stability, makes PIM-PI-8, in particular, an extremely promising candidate for gas separation membranes.…”

Synthetic 6FDA–ODA copolyimide membranes for gas separation and pervaporation: Functional groups and separation properties

“…Relationships between polymer structures and gas separation performances were investigated by some researchers [1,28], but they were not quantitatively described from the effects of functional groups and polymer chains. Fortunately, group contribution methods for prediction of gas permeabilities were developed [29e31].…”

Effects of crosslinking modification on the O2/N2 separation characteristics of poly(phenyl sulfone)/poly(bisphenol A‐co‐4‐nitrophthalic anhydride‐co‐1,3‐phenylenediamine) blend membranes

“…A circular stainless permeability cell (47‐mm disc filters, Millipore, Billerica, MA) was used to measure the transport properties of the membrane. The effective area inside the cell was 17.34 cm 2 ; in addition, O 2 and N 2 with kinetic diameters of 3.46 and 3.64 Å,27, 28 respectively, were tested as penetrants. After both sides of the membrane were evacuated, the pure gas was introduced to the upstream side of the membrane, after which it was allowed to permeate to the downstream side.…”