Selective facilitated fixed-site carrier transport of methanol through sulfonated copolyimide pervaporation membranes for the separation of methanol/toluene mixtures

Dense and asymmetric membranes were obtained from novel sulfonated copolyimide synthesized by polycondensation of 3,3',4,4'-(1,3-diphenoxybenzene) tetracarboxylic dianhydride, 4,4'-bis-dipheny1-2,2'-disulfonic acid and 4,4'-oxydianiline. The polymer was characterized by the use of NMR spectroscopy, differential scanning calorimetry, Fourier transformed infra-red spectroscopy and thermal gravimetric analysis. The morphology of the asymmetric membrane was studied with scanning electron microscopy. Pervaporation separation performance of membranes was studied for H2O/EtOH and MeOH/toluene systems at different compositions and temperatures. Transport of polar components inside the polymer matrix is discussed. The realization of the selective fixed-site carrier transport mechanism for methanol allows reaching high fluxes and separation efficiency values for mixtures with exceeding methanol content. Developed membranes showed great pervaporation performance in the case of MeOH/toluene mixtures separation by reaching a maximal separation factor value of 158 (91 wt% toluene, 20 degrees C, for the dense membrane with total flux of 0.007 kg.m(-2).h(-1)) and maximal overall flux of 1.944 kg.m(-2).h(-1) (36 wt% toluene, 50 degrees C, for the asymmetric membrane with separation factor of 12).