Covalent synthesis of dense zeolite LTA membranes on various 3-chloropropyltrimethoxysilane functionalized supports

A seeding-free synthesis strategy was developed for the preparation of dense and phase-pure zeolite LTA membranes on 3-chloropropyltrimethoxysilane (CPTMS) functionalized supports. Through the functionalization of supports by using CPTMS, the nucleation and growth of a thin, well intergrown zeolite LTA membrane could be promoted on various porous supports such as Al₂O₃ disks and tubes, and TiO₂ disks, as well as on dense supports such as stainless steel, PTFE, and glass disks. The SEM and XRD characterizations indicate that a relative thin but dense and phase-pure zeolite LTA membrane with a thickness of about 3.0μm can be formed on the porous Al₂O₃ and TiO₂ disks by crystallization at 60°C for 24h, and no cracks, pinholes or other defects were observed in the membrane layer. The zeolite LTA membranes prepared on CPTMS-functionalized Al₂O₃ disks were evaluated in single gas permeation and mixed gas separation. It is found that the zeolite LTA membranes prepared on CPTMS-modified Al₂O₃ disks show molecular sieving in gas separation. For binary mixtures at 20°C and 1bar, the mixed gas separation factors of H₂/CO₂, H₂/N₂, H₂/CH₄, H₂/C₃H₈ and H₂/C₃H₆, are found to be 7.4, 6.8, 5.2, 15.3 and 36.8, which are higher than the corresponding Knudsen coefficients.