ABSTRACT
In membrane-based separation, molecular size differences relative to membrane pore sizes govern mass flux and separation efficiency. In applications requiring complex molecular differentiation, such as in natural gas processing, cascaded pore size distributions in membranes allow different permeate molecules to be separated without a reduction in throughput. Here, we report the decoration of microporous polymer membrane surfaces with molecular fluorine. Molecular fluorine penetrates through the microporous interface and reacts with rigid polymeric backbones, resulting in membrane micropores with multimodal pore size distributions. The fluorine acts as angstrom-scale apertures that can be controlled for molecular transport. We achieved a highly effective gas separation performance in several industrially relevant hollow-fibrous modular platform with stable responses over 1 year.
ABSTRACT
Amino functionalized boron nitride nanosheets (FBN) were incorporated into a crosslinked, thermally rearranged polyimide (XTR) to fabricate FBN-XTR nanocomposite membrane. The FBN-XTR membrane exhibited a small decrease in H2 permeability but demonstrated a remarkably increased H2 gas selectivity over other gases, compared with XTR. The XTR membrane heat-treated at 425 °C had a H2 permeability of 210 Barrers and a H2 /CH4 separation factor of 24.1, whereas the nanocomposite membrane with 1â wt % FBN exhibited a H2 permeability of 110 Barrers and H2 /CH4 separation factor of 275, an order of magnitude greater. At 1â wt % FBN loading, the FBN-XTR membrane showed three times higher tensile strength and 60 % higher elongation than pristine XTR membrane. In addition, FBN-XTR was found to be able to be readily processed into thin-film membranes for practical H2 separation applications.
ABSTRACT
Highly permeable, thermally rearranged polymer membranes based on bismaleimide derivatives that exhibit excellent CO2 permeability up to 5440 Barrer with a high BET surface area (1130 m2 g-1) are reported for the first time. In addition, the membranes can be easily used to form semi-interpenetrating networks with other polymers endowing them with superior gas transport properties.
ABSTRACT
A facile two-step synthesis beginning with commercial monomers to prepare copolyimides by Tröger's Base (TB) formation provides membranes for the first time with tunable gas transport relative to hydrogen separations, CO2 plasticization resistance, and good mechanical and thermal properties.
