Preparation of ZSM-5 zeolite membranes by concentration variation with organic-free templates

A new method of preparing ZSM-5 zeolite membranes on the outer surface of porous alpha-Al2O3 tubular by coating 15 nm ZSM-5 seeds without organic templates and then by varying-density synthesis with organic-free template sol-gel was investigated. A template-free nanosized ZSM-5 seeds and synthesis sol-gel of molar composition is 12Na(2)O:100SiO(2):2Al(2)O(3):(2 500 similar to 5 000)H2O. XRD showed that the film was consisted of well-crystallized ZSM-5 zeolite. SEM investigation indicated that the zeolite films on the supports were defect free and the film thickness was approximately 5 mu m. The permeation flux of H-2, N-2 and CO2 0.894, 0.327 and 0.314 mu mol center dot(m(2)center dot s center dot Pa)(-1), respectively. The ideal selectivity of membrane for H-2/CO2, H-2/N-2 was 2.84,2.73, respectively.