(593d) Preparation and Gas Separationperformance of the Inorganic Nano-Particles Carbon Composite Membranes

Carbon membranes, novel materials derived from the pyrolysis of the polymeric precursors, have a well-developed ultramicropore network and exhibit higher gas permeability and selectivity than polymeric membranes. Nevertheless, the gas permeability for pure carbon membranes available now cannot satisfy the requirement of commercial applications due to the disordered inter-connective nano-channels in the pore structure, which results in the high diffusion resistance of the gas molecules penetrating through the membrane.

Incorporating functional materials into membrane precursors to fabricate composite carbon membranes has been regarded as an effective way to tune the disordered pore structure of pure carbon membranes, and thus to greatly improve the gas permeability. In this paper, the inorganic nano-particles/carbon composite membranes with high gas sepraration performance are designed and perpared by incorporating the inorganic nano-particles (nano-oxides, zeolites and ordered mesoporous materials) into the polymeric precursor and pyrolyzing. The effects of species, sizes and pore structure morphology of embeded nano-particls on the structure and gas separation performance of obtained composite carbon membrane are investigated. The as-made composite membranes are characterized by high-resolution transmission electron microscopy (HRTEM), high-resolution scanning electron microscopy (HRSEM), X-ray diffraction (XRD) and N₂ adsorption, of which the gas separation performance in terms of gas permeability and selectivity are evaluated using the single gas (H₂, CO_2, O₂, N_2, CH₄) and gas mixtures (CO₂/N₂ and CO₂/CH₄, 50/50 mol.%). The results indicate that the gas permeability of inorganic nano-particles/carbon composite membranes are enhanced by 3-10 times compared with the pure carbon membranes, which is attributed to the additonal channels for promoting gas diffusion created by the dispersion of nano-particles, involving the micro-interfacial gaps (interfacial pores) and the inner ordered channels of the porous particles. The nano-particles with small particle sizes, large pore channels and three dimensional pore structure would be benificial to enhancing the gas permeability and maintaining the high gas selectivity of the obtained composite carbon membranes, wihich suggests that the gas separation performance is controlled by porous structure of the nano-particles/carbon composite membranes tuned by changing the properties of the embeded nano-particles. The composite carbon membranes have both the higher permeability and selectivity with porous particles (zeolites and ordered mesoporous materials). The gas diffusion mechanism and the relevant model of gas diffusion pathways in the nano-particles/carbon composite membranes is also discussed.