| Carbon membranes are prepared by high temperature carbonization of macromolecular materials containing carbonaceous species, which can effectively separate mixture by the domination of molecular sieving mechanism. Compared with organic membranes, carbon membranes take the advantages of high selective permeation, excellent heat resistance, chemical stability and mechanical strength. Carbon membranes have shown broad application prospects in the fields of gas separation, liquid separation, membrane catalysis and biomass purification, etc. Therefore, the research of carbon membranes has become one of the hottest topics at present. However, the disadvantages of homogeneous carbon membranes, i.e., brittle and fragile, have seriously hindered their industrialization process for the difficult to meet the requirements of industrial production. Regarding this, high mechanical carbon membranes were prepared on the surface of carbonaceous support through spin-coating method. Besides, catalytic separation carbon membranes were also produced in order to promote the development of carbon membranes on the field of membrane catalysis reaction. We believe that the present work would build solid foundation on the development of carbon membranes in association with application value and commercialization.In this thesis, the effect of preheat treatment at 280oC and incorporation of copper-based catalyst on the porous structure and membrane-formation was investigated using phenolic resin as raw material. Supported carbon membranes were prepared through spin-coating method using 1,4-bis(4-amino-2-trifluoromethylphenoxy) benzene- 1,2,3,4-cyclobutanetetracar- boxylic dianhydride(6FAPB-CBDA) type polyimide as the precursor of selective layer of carbon membranes, catalysts as dopant. Thermogravimetry, Fourier transformed infrared spectroscopy, x-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and gas permeation, were utilized to respectively analyze the thermal stability of precursor, evolution of functional groups, microstructure, morphology, surface element valence and separation performance of the samples. The effects of permeation temperature, permeation pressure and catalysts content on the gas separation performance of carbon membranes were studied. Finally, carbon membrane was coupled into reactor to enhance the reaction of methanol steam reforming, and the effects of reaction temperature, catalyst formula, downstream purging and carbon membranes on the methanol conversion and hydrogen yield were investigated.Results have showed that:(1) It found that the pore radius distribution of support is more uniform centering in the range of 0.35-0.42μm along with the porosity of 38.13%, which is formed by preheat treatment at 280oC and carbonization at 650oC. In addition, the introduction of catalyst would diminish the mechanical strength of support, together with the enlargement of pore radius and porosity.(2) As for supported carbon membranes prepared by spin-coating method at the optimum 4 times coating, the permeability of H2, CO2, O2 and N2 were respectively 138.82 Barrer, 28.25 Barrer, 20.91 Barrer and 2.63 Barrer, along with the selectivity of H2/N2, CO2/N2 and O2/N2 were respectively 52.8, 10.7 and 8.0.(3) When carbon membranes were incorporated with catalyst, their gas permeability and selectivity decreased. Furthermore, with the increase of the doping amount, the gas permeability first decreased and then increased.(4) In the case of reaction of methanol steam reforming for hydrogen production, the best reaction temperature is 240oC, and the best formula for copper-based catalyst is sodium carbonate in excess of 20%. Among the membrane coupled reactors, i.e., the pure supported carbon membranes, catalytic hybrid carbon membranes and catalytic carbon membranes, catalytic carbon membranes exhibit the best efficiency. That is, the methanol conversion rate is 69.8% and the hydrogen yield is 49.1%. Compared with the fixed length reactor, the hydrogen yield is increased by 67.6%. |
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