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 3.0 μm can be formed on the porous Al2O3 and TiO2 disks by crystallization at 60 °C for 24 h, 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 1 bar, 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.