| The separation of aromatic/aliphatic is one of the most important and difficult process in chemical and petrochemical industry, while traditional separation techniques including azeotropic and extraction can not obtain effective performance because of the close physical and chemical properties of aromatics and aliphatics. Membrane pervaporation technique has wide prospect for its high efficiency, low energy consumption and enviromental friendly characters. The membrane performance mainly depends on the dissolution and diffusion properties between polymer and solvents, hence the membrane material and the preparation method are the key of pervaporation performance. The polymers used for aromatic/aliphatic separation are always synthesized complicated, and much organic solvents are introduced during the preparation process. Besides, the membranes easily get swollen and lead to rapid decline of performance. Then it’s important to explore novel membrane materials and improve the stability of aromatic/aliphatic pervaporation membrane.In this study, commercial block copolymer PEBA and amphiphilic hyperbranched polymer W3000 were chosen as the membrane materials. The abundant functional groups of the polymers have interaction with the aromatics. Meanwhile, inorganic Al2O3 ceramic substrate was used for its high mechanical strength to prepare composite membrane. By thermal crosslinking treatment, the polymer chains interact and a dense and stable structure was formed. Through different characterization, the microstructure of the substrate and composite membrane were investigated. The performance of separation of aromatic/aliphatic mixtures was also determined.Based on the solution-diffusion mechanism, the IGC experiment was carried out to study the solubility and diffusivity of toluene, n-heptane towards PEBA. Dip-coating method was used to fabricate PEBA/ceramic composite membrane, and a dense layer was formed after crosslinking which was characterized by FTIR. The effect of PEBA concentration, thermal crosslinking temperature and time, the temperature and content of the feed on membrane performance was investigated. And the stability of the composite membrane was determined. In 400 C, for 50 wt % toluene/n-heptane mixture, the optimal separation factor was 4.3 and the permeate flux was 65.0g/(m2h) by PEBA/ceramic membrane. The thermal crosslinked PEBA/ceramic composite membrane exhibited high stability in 30 h continuously working.The hyperbaranched polymer W3000 has abundant hydrophilic and hydrophobic chains, which makes it easily emulsified in water. The W3000 emulsion particles formed in different concentration were observed by TEM. The W3000 emulsion particles were assembled in the pores of the substrate by a press-driven method, and a dense layer was formed after thermal-crosslinking. The morphology of the membranes prepared by solvents of DMF and water were observed by SEM. Crosslinking density were examined to investigate the effect of solvents on permeate flux. The effect of preparation conditions and operation conditions on the performance of pervaporation were investigated. In 400 C, for 50 wt % toluene/n-heptane mixture, the optimum membrane exhibited a separation factor of 4.2 and a permeate flux of 238.0g/(m2h). The composite membrane showed excellent stability in 240 h continuous swelling in the feed. |
