NaA zeolite membranes on modified porous stainless steel supports: a comparative study of different SiO 2 sources

The deposition of a NaA zeolite layer on porous stainless steel substrates was optimized in order to obtain composite membranes for hydrogen separation. The effect of the silica source on NaA zeolite crystallinity and morphology was studied using two synthesis routes: concentrated gel and clear solution. The optimized synthesis conditions were applied for the synthesis of NaA zeolite layers on top of porous stainless steel disks or on the outer surface of tubular supports. SEM and XRD measurements confirmed that the use of rice husk allowed obtaining defect free and pure phase NaA zeolite membranes. Selectivity values similar to those published for NaA zeolite membranes based on ceramic substrates were obtained using zeolite layers deposited on porous stainless steel tubes. From the curve fitting of the experimental data, the contribution of zeolitic and non-zeolitic flux was estimated. For the membranes synthesized from a concentrated gel, H 2 showed a predominated contribution of the zeolitic flux.