Application of ionic liquid-polymer gel membrane in toluene/n-heptane separation

The separation of aromatic and alkane is one of the most important and challenge chemical separation process. This study reports the high-efficiency separation of aromatics/alkanes in the pervaporation process based on a series of novel ionic liquid gel membranes. The ionic liquid gel membrane was characterized by FT-IR, SEM, AFM, TGA, and XRD techniques. The results revealed that the IL was maintained in the three-dimensional structure of polymer support and the membrane kept its stability when the temperature was over 300 degrees C. The relevant parameters i.e. polymer concentration, IL concentration, IL type, film-forming temperature, membrane thickness, feed concentration, operating temperature and feed flow rate on membrane process were investigated. The optimal membrane was prepared when the P(VDF-HFP) and [Amim][Tf2N] concentrations were 15 wt% and 45 wt%, the film-forming temperature was 15 degrees C and the membrane thickness was 120 mu m. When the initial toluene concentration was 50 wt% and the flow rate was 200 mL/min, the best flux (120 g.m(-2).h(-1)) and separation factor (11.3) were observed at 25 degrees C. Moreover, the separation factor was over 10 and the flux maintained at the same level after working continuously for 30 h, which indicates that the membrane has good stability.