Coupling microwave-assisted and classical heating methods for scaling-up MFI zeolite membrane synthesis

Silicalite-1 (S-1) nano-seeds obtained by microwave-assisted (MW) heating have been used to coat industrial supports and to up-scale the synthesis of MFI zeolite membranes by secondary growth applying a classical heating (CH) method. The MW-assisted method was adapted/optimized for fast synthesis and high yield of uniform and non-aggregated S-1 nano-seeds suspensions which were directly used for seeding macroporous industrial α-Al2O3- based supports by dip-coating. The CH secondary growth yielded uniform MFI membranes, by applying optimal reaction conditions while minimizing the reaction time and consumption of chemicals. The protocol coupling MW-assisted and classical heating in zeolite membrane synthesis revealed high reproducibility and has been validated on various industrial ceramic supports: single tubes (Pall-Exekia, Atech, Inocermic, CTI) and also single capillaries and capillary bundles, from Hyflux, providing a higher surface/volume ratio (typically S/V > 100 m2/m3). Membrane homogeneity has been validated by both SEM and single gas permeation measurements with N2 and SF6. The N2/SF6 ideal selectivity was used to predict the ethanol/water separation factor for the prepared MFI membranes.