Facile synthesis of zeolite FAU molecular sieve membranes on bio-adhesive polydopamine modified Al2O3 tubes

A seeding-free synthesis strategy was developed for the preparation of dense and phase-pure zeolite FAU membranes through mussel-inspired polydopamine (PDA) modification of porous Al 2 O 3 tubes. Zeolite FAU nutrients can be attracted and bound to the support surface via the formation of strong non-covalent and covalent chemical bonds, thus promoting the nucleation and growth of uniform, well-intergrown and phase-pure zeolite FAU membranes. The SEM and XRD characterizations demonstrate that a relative thin but dense and pure-phase zeolite FAU membrane with a thickness of about 2.3   µm can be obtained on the PDA-modified Al 2 O 3 tube after crystallization at 75   °C for 24   h, and no visible cracks, pinholes or other defects are observed on the membrane layer. The zeolite FAU membrane prepared at 75   °C for 24   h was evaluated in single gas permeation and mixed gas separation. For binary mixtures at 50   °C and 1   bar, the mixture separation factors of H 2 /CH 4 and H 2 /C 3 H 8 are 9.9 and 127.7, respectively, which are much higher than the corresponding Knudsen coefficients. And relative high H 2 permeance of about 1.9×10 −7   mol   m −2   s −1   Pa −1 can be obtained through the FAU membrane due to the thin layer and the relative wide pore size of 0.74   nm, demonstrating a viable direction for promising application of FAU membranes in hydrogen purification and separation.