Temperature stable, polymeric thin-film composite membrane for hydrogen separation

The high temperatures and aggressive chemical conditions of many relevant industrial processes such as the hydrogen production from hydrocarbon fuel sources restrict the use of polymeric membranes for gas separations (GS) that could make such processes more efficient and environmentally friendlier whilst reducing their operational costs. Therefore, this work was centered on the development of a thin-film composite membrane (TFCM) prepared with high-performance polymeric materials capable of withstanding temperatures above 200 °C in industrial GS applications and which could eventually be integrated to perform in situ separations in a reactor. An innovative prototypical three-layered TFCM featuring the polyimide 6FDA-6FpDA as selective layer deposited on a cross-linked (CL) Matrimid® 5218 (Matrimid) porous support prepared on a thermally stable polyphenylene sulfide (PPS) nonwoven was investigated in two different gas permeation experimental facilities in a range from 30 to 200 °C and feed pressures of up to 10 bar. The TFCM exhibited low permeances compensated by outstanding ideal selectivities for H2/CO2, H2/CH4 and O2/N2 gas pairs. This behavior was attributed to the formation of an interpenetrating network between 6FDA-6FpDA and Matrimid, caused by a swelling effect of the solvent used to form the selective layer on the surface of the cross-linked Matrimid porous membrane. A drop in membrane performance was observed above 170 °C due to a reduction in the thermal stability of the CL Matrimid resulting from the opening of the imide rings of the polyimide backbone during the cross-linking reaction.