Fabrication And Performance Study Of The Nanoporous Carbon Membranes

Nanoporous carbon membranes were prepared by carbonizing polymers at hightemperature through two different methods and its separation performance wasinvestigated for small molecules gases, such as H₂, He, CO₂, N₂, CH₄. Meanwhile,ideal separation factor were calculated, base on the permeance of pure gases.Stainless steel tube and α–Al2O3 tube modified and cleaned by means of sol-geltechnique were chosen as supports. Nanoporous carbon membranes were preparedthrough pyrolyzing precursor (polyimide with N-methyl-pyrrolidone as solvents) at600°C-700°C under the condition of flowing nitrogen gas (flow rate: 45ml/min). Theinfluence of carbonation condition on separation performance were investigated, theresults showed that the diffusion of gas through the membrane was mainly controlledby the mechanism of Knudsen diffusion.Dissolving Ni(NO₃)₂·6H₂O in polyimide and N-methyl-pyrrolidone, withmodified α–Al₂O₃ tube as support, nanoporous carbon membranes were prepared bymeans of the combination of the carbonizing at high temperature with catalyticdecomposition of methane using the Ni/polyimide as template. The differencebetween nanoporous carbon membranes with nickel and without nickel showed thatthe introduction of nickel improves the structure of membrane and lower the time andcosts. Meanwhile, ideal separation factor of H₂/N₂ , H₂/CH₄ were 8.4 and 14, largerthan theoretical value of Knudsen diffusion. Diffusion of gas through the membranewas mainly controlled by the mechanism of molecular sieving.Support,precursor and nanoporous carbon membranes were characterized byFT-IR, XRD and SEM-EDX. The effect of the temperature and pressure on thepermeance of gases was investigated.