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Template-free nanosized ZSM-5 seeds with an average size of 15 nm were prepared from a synthesis solution with the composition 12Na2O∶100SiO2∶2Al2O3∶2500H2O. By the use of these seeds, thin ZSM-5 zeolite membranes were prepared on the outer surface of a porous α-alumina tube with a pore size of 2 μm in a gel system by varying-concentration synthesis with organic-free template. The first composition synthesis sol-gel was the same as seeds of molar composition and the second one was 12Na2O∶100SiO2∶2Al2O3∶5000H2O at 180 ℃ for 10 h, respectively. XRD shows that the film consists of well-crystallized ZSM-5 zeolite. SEM investigation indicats that the zeolite films on the supports are defect free and the film thickness is approximately 8 μm. The permeances for H2, N2, CH4 and CO2 are 8.94×10-7, 3.27×10-7, 3.9×10-7, 3.14×10-7 and 0.874×10-7 mol·m2·s-1·Pa-1, respectively. The ideal selectivity of membrane at room temperature for H2/CO2, H2/N2, H2/CH4 are 2.84, 2.73 and 2.29, respectively.
Template-free nanosized ZSM-5 seeds with an average size of 15 nm were prepared from a synthesis solution with the composition 12Na2O: 100SiO2: 2Al2O3: 2500H2O. By the use of these seeds, thin ZSM-5 zeolite membranes were prepared on the outer surface of a porous α-alumina tube with a pore size of 2 μm in a gel system by varying-concentration synthesis with organic-free template. The first composition synthesis sol-gel was the same as seeds of molar composition and the second one was XRD shows that the film consists of well-crystallized ZSM-5 zeolite. SEM investigation indicats that the zeolite films on the supports are defect free and the film thickness is approximately either 8 μm. The permeances for H2, N2, CH4 and CO2 are 8.94 × 10-7, 3.27 × 10-7, 3.9 × 10-7, 3.14 × 10-7 and 0.874 × 10-7 mol · m2 · s-1 · Pa-1, respectively. The ideal selectivity of membrane at room temperature for H2 / CO2, H2 / N2, H2 / CH4 are 2.84, 2.73 and 2.29, respectively.