Abstract: Vertically aligned carbon nanotube(CNT) arrays were grown on porous Al₂O₃ substrate by improved floating catalysis method. Gaps among CNTs were sealed by polystyrene using spin-coating method, and then, the sample was prepared into carbon nanotube composite membrane. H₂ and CO₂ permeation through the prepared carbon nanotube membrane were studied. Experimental results show that the ideal selectivity of H₂/CO₂ increases with the decreasing of carbon nanotube diameter, it is higher than Knudsen limit in the membrane with smaller diameter carbon nanotubes, the ideal selectivity reaches to 6.25, gaining preferable separation results. Permeance of both gases slightly decreases when permeation temperature increases.

Key words: Carbon nanotube composite membrane, Permeance, Floating catalysis method