Gas permselectivity properties of PBI-based asymmetric flat and hollow fiber membranes for H2/CO2 separation

Two different membrane configurations, flat membranes and hollow fiber membranes were studied for H2/CO2 gas separation. In chapter 2, an asymmetric flat membrane consisting of a thin, spin-coated layer of polybenzimidazole (PBI) on a 26 wt% zeolitic imidazolate framework-8 (ZIF-8)/PBI mixed-matrix membrane (MMM) is described. The surface was modified to improve the ideal selectivity of the MMM substrate without reducing the flux. The performance of MMMs with a 2.5 microm PBI skin providing a H 2 permeability of 3.66 Barrers and an ideal H2/CO2 selectivity of 29 is located above the Robeson upper bound. In chapter 3, PBI hollow fibers are described that were fabricated using different spinning conditions to obtain flexible membranes for H2/CO2 separation. Hollow fibers were assembled into modules and then tested at different temperatures (up to 300 °C) and different pressures (up to 15 atm). The best permselectivity results are higher than published PBI hollow fiber performance.