Journal
JOURNAL OF MEMBRANE SCIENCE
Volume 563, Issue -, Pages 726-733Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.memsci.2018.06.033
Keywords
Homogeneous blend; Double crosslinking; Gas separation; Fractional free volume (FFV); Hydrogen purification; CO2 capture
Categories
Funding
- BASF SE, Germany [R-279-000-411-597]
- National University of Singapore
- Dean's Office of Faculty of Engineering for the project entitled Natural Gas Centre [R-261-508-001-646]
- Department of Chemical and Biomolecular Engineering for the project Membrane Research for CO2 Capture [R-279-000-505133]
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This study, for the first time, demonstrates a new double-crosslinking approach to manipulate the microstructure and gas separation performance of PBI membranes for H-2/CO2 separation at 150 degrees C. The PBI membranes were firstly blended with sulfonated polyphenylsulfone (sPPSU) as an ionic-crosslinker and then alpha,alpha'-dibromo-p-xylene (DBX) as a covalent crosslinker with the aid of thermal annealing. Experiments show that PBI and sPPSU interact on the molecular level. Different from conventional blends, the PBI/sPPSU blend membranes show both enhanced chemical resistance and greater fractional free volume (FFV) after annealing at elevated temperatures because of chain motion and ionic crosslinking. As a result, the blend membranes maintain their high permeability after annealing. The DBX addition further improves the chemical resistance and tightens the inter-chain spacing that results in membranes with a small FFV and pore size. Consequently, the DBX cross-linked blend membranes retain their high gas pair selectivity at high temperatures. The 50/50 PBI/sPPSU blend membrane crosslinked by 0.7 wt% DBX at 300 degrees C possesses the best separation performance surpassing the Robeson's upper bound. It has an impressively H-2 permeability of 46.2 Barrer and a high H-2/CO2 selectivity of 9.9 at 150 degrees C.
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