Nanocomposite MFI-alumina hollow fibre membranes prepared via pore-plugging synthesis: Influence of the porous structure of hollow fibres on the gas/vapour separation performance

One major drawback in the synthesis of zeolite membranes is the lack of reproducibility ascribed to the support quality. In this paper, a gas–liquid displacement technique was used prior to pore-plugging hydrothermal synthesis to evaluate the quality of hollow fibre supports in terms of pore size distribution of surface pores. Using these supports, four nanocomposite MFI-hollow fibre membrane families were identified, showing different gas/vapour separation performance. The effective MFI thickness of these membranes (0.6–1.2 μm) was computed from pure N2 and CO2 permeance using Maxwell–Stefan modelling, while their separation performance was evaluated in the separation of n-butane/H2, CO2/N2 and ternary xylene isomer mixtures. The MFI-alumina hollow fibres displaying the best quality corresponded to those synthesized using hollow fibres with surface pore size distributions centred at 0.2 μm, suggesting more efficient pore plugging. Grain boundaries between nearby zeolite crystals only appear to play a role in the case of xylene isomer separation.