Preparation And Characterization Of Ordered Nanoporous Carbon Membranes

As a class of novel porous membrane material, carbon membrane exhibits promising prospect in various fields, such as oxygen enrichment, hydrogen recovery, acid gas removal, dehydration, helium preparation and membrane reactor, etc. Carbon membranes have the advantages of high selectivity, thermal stability and corrosion resistance, besides the virtues of other traditional membranes. Before industrial applications in large scale, a series of key issues confronted by carbon membranes should be solved, in order to improve the cost performance and competitiveness, such as the complex preparation, unable repetitive usage, high cost and inferior resist compression. There is a well-kown common rules that the performance and application of materials are inheritly depended on their intrisic structure. In this thesis, the preparations of ordered nanoporous carbon membrane (ONCM) with regular microstructure were proposed in the view point of solving the restricted problems in a certain extent. It is expected that the resutls can provide the support for the theory of carbon fabrication to further expanding aspects of the carbon application.Here, two preparation methods i.e., soft template and hard template, were raised to fabricate ONCM. Many advanced techniques, such as TGA, FTIR, SEM, FE-SEM, TEM, XRD, SAXD, bubble pressure and permeation, etc., were used to analysis the thermal stability, functional group evolution of precursors, micro/macro feature, pore structure, carbon structure and gas separation ability of ONCM. In the case of soft template method, triple–copolymer F127 (PEO-PPO-PEO) was used as template agent and phenolic resin (PR), respectively. The effects of some important factors including precursor synthesis conditions and membrane formation support were investigated on the porous structure and performance. In the case of hard template method, tetraethoxysilane (TEOS) and silica (SBA-15) were adopted as template agents in PR sol or polyimide prepolymer solution, respectively. Finally, ONCM were prepared after the processes of membrane formation, carbonization and template removal. The results have shown that ONCM can be successfully prepared by correspondingly using block compolymer F127 and mesoporous silica as soft template and hard template, phenolic resin and polyimide prepolymer as membrane casting solution, through the processes of self-assembly, membrane formation, carbonization and template removal. When NaOH used as catalyst, defect-free ONCM with the porous diameter circa 9nm could be formed in large area. However, under the condition of acid catalyst, large area ONCM also can be obtained with the pore diameter of 11nm by attaching to support. When the phenoic resin green membrane matrix was used as support, the as-prepared ONCM exhibits the gas separation performance for H2/N2, CO2/N2 and O2/N2 as 3.74, 0.80 and 0.94, respectively. That markedly exceeds the domain of kundsen diffusion. Large area ONCM cannot directly obtained by one-pot hard-template method. ONCM prepared by two-step method has the average pore size about 9nm and the H2/N2 separation factor of 4.6.