| Polyimide(PI) membranes were prepared through polyamic acid solution via a phase inversion method for pervaporation of octane/thiophene mixtures, using precursors of pyromellitic dianhydride, 4,4'-diaminodiphenyl ether and 3,5-diamino- benzoic acid(DABA). PI membranes were characterized by FT-IR, SEM, XRD and DSC. Effects of the polymerization temperature, composition of the gelation agent, transport agent and content of DABA on the performance of PI membranes were evaluated experimentally. Major conclucions obtained were listed as below.Polyimide precursors were synthesized at different temperature ranged from 0℃to 40℃followed by the treatment in the gelation agent composed of 35vol.% ethanol and 65vol.% water to prepare PI membranes. It is indicated that PI membrane synthesized at 30℃has the optimal separation performance for pervaporation of octane/thiophene mixtures with the flux of 1.84 kg/m2h and the separation factor of 3.03 for thiophene.Polyimide membranes were prepared in different gelation agent containing various ethanol contents ranged from 5% to 35% and water under the same reaction temperature of 30℃. It is indicated that the membrane prepared in the gelation agent composed of 15vol.% ethanol has the optimal separation performance for pervaporation of octane/thiophene mixtures with the flux of 2.36 kg/m2h and separation factor of 3.16 for thiophene.Transport agent of ethnol in the feed mixture can effectively improve the separation performance of PI membranes. It is indicated that addition of transport agent increases obviously the flux and the separation factor.It increase the permeation of thiophene while the flux decreases as the content of ethanol decreases in the feed.Finally, another polyimide membranes were synthesized introducing the third monomer of DABA with a molar concentration of 5~20%. It is indicated that this kind of PI membrane has the optimal flux of 1.03 kg/m2h and the separation factor of 5.0 when DABA content is 5%.
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