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

Abstract

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 °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 °C and the membrane thickness was 120 μm. 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 °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.