ZSM-5 zeolite membranes prepared on porous α-Al2O3 tube from a template-free crystallization gel

ZSM-5 zeolite membranes synthesized on rough porous α-Al2O3 tubes with an average pore size of 2 μm in the absence of organic template crystallization gel were investigated. The molar composition of nanosized ZSM-5 seeds was 9TPAOH:25TEOS:0.25 Al2O3:480 H2O. Porous α-Al2O3 tubes were seeded with these colloidal TPA-silicalite-1 crystals with a size of 90-100 nm. The seeded supports were calcined in accordance with DTA/TG of nanosized ZSM-5 and treated in a synthesis sol-gel to grow the seed crystals into ZSM-5 membranes on the outer surface of porous α-Al2O3 tubes. The molar composition of the crystallization gel without organic templates was 67Na2O:Al2O3: 240SiO2:6000 H2O. XRD patterns show that the film consists of well-crystallized ZSM-5 zeolite. SEM investigation indicates that the zeolite films on the supports are defect free and that the film thickness is approximately 8 μm. The permeability for H2 is 1.50 × 10-6 mol·m-2· s-1·Pa-1 and the ideal separation factor for H2/N2 is about 3.85.