Hydrogen Separation at High Temperature with Dense and Asymmetric Membranes based on PIM-EA(H2)-TB/PBI Blends

The preparation of dense and asymmetric flat membranes from the blending of
polybenzimidazole (PBI) and (1.5-20 wt%) of a polymer of intrinsic microporosity (PIM-EA(H2)-TB) is reported. Thermal characterization validated the blend by revealing a single glass transition temperature, which suggests the absence of polymer phase segregation. In addition, the decomposition activation energy and d-spacing of the blends follow trends that correlate with the amount of the PIM
component. The membranes have been tested for the separation of H2/CO2 mixtures. The properties of the dense membranes, which also incorporate zeolitic imidazolate-8 (ZIF-8) nanoparticles, helped understanding of the behavior of the PIM/PBI blends by which phase inversion results in high separation performance asymmetric membranes. Asymmetric membranes show H2/CO2 selectivities of 23.8 (10/90 wt% PIM/PBI) and 19.4 (20/80 wt% PIM/PBI) together with respective H2 permeances of 57.9 and 83.5 GPU at 250 °C and 6 bar feed pressure. The gas separation performance of these asymmetric blends has been fitted to an empirical model, showing the influence of the amount of PIM and the feed pressure.