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

Abstract

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 Al2O3 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 2.3µm can be obtained on the PDA-modified Al2O3 tube after crystallization at 75°C for 24h, and no visible cracks, pinholes or other defects are observed on the membrane layer. The zeolite FAU membrane prepared at 75°C for 24h was evaluated in single gas permeation and mixed gas separation. For binary mixtures at 50°C and 1bar, the mixture separation factors of H2/CH4 and H2/C3H8 are 9.9 and 127.7, respectively, which are much higher than the corresponding Knudsen coefficients. And relative high H2 permeance of about 1.9×10−7molm−2s−1Pa−1 can be obtained through the FAU membrane due to the thin layer and the relative wide pore size of 0.74nm, demonstrating a viable direction for promising application of FAU membranes in hydrogen purification and separation.