Fabrication Of Functional Carbon Membranes Hybridized By Iron Compounds And Their Gas Separation Performance

Carbon membrane is a novel membrane material consisted of microporous carbon matrix in these two decades. It shows high selectivity in gas separation by molecular sieve because of its super microporous. Furthermore, it has good thermal stability and good chemical stability. It is regarded as the most promising gas separation membrane. However, the low gas permeability and high cost of the carbon membrane make it not satisfy the industry requirement. Thus, it is very important to design and optimize the structure of the precursor to synthesis high performance functional carbon membranes.Functional carbon membranes for gas separation were designed and prepared by incorporating Fe₃O₄,γ-Fe₂O₃, Zn_0.5Ni_0.5Fe₂O₄ nanoparticles and ferrocene into polyimide, used as the precursor of carbon membrane in this work, respectively. The characterizations of the as-synthesized membranes were studied by XRD, TEM, FTIR and VSM. The effects of kinds of doping agents, doping amount, permeating temperature and pyrolytic temperature on the gas permeation of functional carbon membranes were mainly investigated by gas permeation GC coupling technique.Gas permeation test results show that all the functional carbon membranes' gas permeation has improved a lot compared to pure carbon membrane, especially to micromolecule gas H₂ whose permeability is improved by nearly 61 times at most. The permeabilities of pure gas H₂, CO₂, O₂, N₂, CH₄ in functional carbon membrane with 20wt.% Fe₃O₄ addition are 15476,4385,1565,193å’Œ114 barrer respecticvely. With the increase of the dopant amount exceptγ-Fe₂O₃, the gas permeability of the functional carbon membranes increases, while, the selectivity decreases. Polyminde/ferrocene-carbonized membrane' gas performance is influenced by permeating temperature, not related to feed pressure. Gas performance of functional carbon membrane derived from doing Fe₃O₄ has a remarkable degradation as pyrolytic temperature increases.α-Fe nanoparticles are well-distributed in carbon matrix derived from ferrocene' decomposition during the pyrolysis process. Fe₃O₄,γ-Fe₂O₃ and Zn_0.5Ni_0.5Fe₂O₄ nanoparticles transform into other phase morphologies after pyrolysis, meanwhile, Fe₃O₄ and Zn_0.5Ni_0.5Fe₂O₄ are influential in the formation of graphitizable carbon (called "catalytic carbonization and graphitization") from precursor during the pyrolysis process. Carbon matrix exists in the forms of graphite-like layers and turbostratic carbon structure. VSM tests shows that functional carbon membranes prepared by incorporating Fe₃O₄,γ-Fe₂O₃, Zn_0.5Ni_0.5Fe₂O₄ nanoparticles belong to the soft magnetic materials and have a good property of magnetic response. Their magnetic properties are obviously influenced by the dopant amount.