Preparation And Study On Gas Separation Performance Of Novel Carbon Membrane

In next several dozens years, the gas separation membrane’s industrialization market demand willgrow largely. This kind of expansion depends to a great extent on the continuous development of highefficiency membrane. Because the current polymer membrane limited to the relation between thepermeability and the selectivity, has been restricted its application to the gas separation, the inorganicmembrane is blooming. The carbon membrane, one kind of highly effective energy conservation newmaterial which can be used in the gas separation, belongs to one kind of porous inorganic membrane.The good carbon membrane is prepared by the pyrolysis of a suitable polymeric precursor under thecontrolled conditions. The carbon membrane becomes more and more important under the new timesseparation membrane technology, because they have the high selectivity, the permeability and thestability under the corrosive and high temperature operation’s conditions. In addition, the carbonmembrane has the enormous industrialization application potential in the gas separation.A type of carbon molecular sieve gas separation membranes is synthesized at pyrolysistemperatures by dip-coating a commercial polyetherimide （PEI） precursor on a porous ZrO₂-Al₂O₃composite sol-modified alumina support and further treated by pre-oxidation in air. The effects of thedifferent properties of supports, the concentration of precursor solution, coating times, pretreatmentconditions and carbonization temperatures on the microstructure and gas separation performance ofcarbon membranes are investigated, respectively and the optimum conditions of preparing PEI basedcarbon membranes are determined. To investigate the influence of carbonization temperature on thecarbon membrane structure and gas separation performance, thermal gravimetric analysis （TG）,Fourier transform infrared spectroscopy （FT-IR）, Raman spectroscopy （Raman）, X-ray diffraction（XRD）, scanning electron microscopy （SEM） and gas permeability tests are employed tosystematically study the thermalstability of polymer film during the pyrolysis, chemical structure ofcarbon films, carbon microcrystalline structure and graphitization evolution, surface morphologystudies and gas separation properties. The results indicate that the carbon membranes derived fromdifferent carbonization temperatures possess the different physical and chemical structure, carbonstructures and pore structure, which affect the permeability and selectivity of the carbon molecularsieve gas separation membranes.In order to further improve gas separation performance of carbon membrane, the carbonmembranes are modified by blending zeolite3A and tetraethoxysilane into the membrane precursors.The results show that the forming-membrane performance and gas permselectivity of the carbonmembranes are improved, respectively. When the3A/C hybrid membranes are prepared at600℃, theideal separation factors of H₂/N₂and CO₂/N₂reached13and5.2, respectively; and when the Si/Chybrid membranes are prepared at600℃, the ideal separation factors of H₂/N₂and CO₂/N₂reached21.97and7.14, respectively. The separation factors of these two kinds of hybrid membranes are largerthan the theoretical value of Knudsen diffusion, respectively, which indicats that gas diffusion throughthe membrane is mainly controlled by the mechanism of molecular sieving. In addition, hybrid carbonmembranes are characterized by XRD, SEM-EDS and gas permeability tests.