Preparation Of Nano-particles Filled Tubular Carbon Molecular Sieve Membranes

Carbon molecular sieve (CMS) membranes have attracted much attention becauseof their good separation ability for gas mixtures. Nowadays, there are commercialhollow fiber CMS membranes in Israel and a pilot plant has been demonstrated in theUS using supported CMS membranes to enrich H2. However, the gas permeancesthrough CMS membranes are still low and have to be enhanced. It is reported inliterature that the gas separation ability can be enhanced by filling nano-inorganicparticles into the gas separation membranes. Research on nano-particle filled gasseparation membranes is mainly focused on polymeric membranes. However it israrely reported for the preparation of gas separation inorganic membranes filled withnano-sized with particles.In this thesis, nano-sized Ni and NaA zeolite particles filled CMS membranes werefabricated on tubular porous Al2O3 supports, by using phenolic resin as carbon source,in an attempt to prepare membranes for the separation of different gas pairs. Variousfactors for the preparation of the membranes were examined and the membranes werecharacterized by scanning electron microscopy and energy dispersive x-ray analysis.First, pure CMS membranes were prepared by dip-coating combined withultrasound technique in order to determine the optimum preparation conditions. Theinfluence of some factors, such as the pore size of substrates, solution concentrationand coating cycles, were investigated. It was found that the CMS membrane preparedwith 4 cycles of dip-coating process showed a CO2 permeance of 1.1×10-9mol·m-2·s-1·Pa-1, a permselectivity of 300 for CO2/CH4 and 6.8 for O2/N2 at 60oC.Then, Ni-filled CMS membranes were prepared by adding nano-sized nickelparticles into the coating solution and using the method for the preparation of pureCMS membranes. It was found that the content of nickel in the coating solutionexerted affects on the performance of membranes. Ni-CMS membranes prepared with1~3wt% Ni coating solution showed good separation selectivity for O2 over N2 (O2permeance: 5.7×10-10 mol·m-2·s-1·Pa-1, O2/N2 separation factor: 11) and CO2 over N2(CO2 permeance: 2.5×10-9 mol·m-2·s-1·Pa-1, CO2/N2 separation factor: 48). On theother hand, Ni-CMS membranes prepared with 5wt% Ni coating solution exhibitedmuch less CO2/N2 permselectivity (CO2 permeance: 3.0×10-9mol·m-2·s-1·Pa-1, CO2/N2separation factor: 4.4), but showed much better CO2/H2 permselectivity (CO2/H2separation factor: 39), which indicated that higher Ni content favored the diffusion of ⅡAbstractCO2 and blocked the diffusion of H2 through the membranes.Finally, CMS membranes filled with nano-sized NaA zeolites were prepared andcharacterized by scanning electron microscopy. It was found that less coating cycleswere needed to prepare the zeolite-filled CMS membranes, which showed almostidentical permselectivity of CO2/N2 to pure CMS membranes. Nano-sized NaAzeolite-filled CMS membranes prepared with 2wt% NaA in coating solution and 2cycles of dip-coating process exhibited good separation ability for CO2/N2 (CO2permeance: 2.7×10-9 mol·m-2·s-1·Pa-1, CO2/N2 separation factor: 54) and O2/N2 (O2permeance: 8.1×10-10 mol·m-2·s-1·Pa-1, O2/N2 separation factor: 16). The permeance ofCO2 was higher than that through the prue CMS membranes when the selectivity ofCO2/N2 was close.