Role of ionic liquids in enhancing the performance of the polymer/AgCF3SO3/Al(NO3)3 complex for separation of propylene/propane mixture

In this study, the role of ionic liquid 1-butyl-3-methyl imidazolium tetrafluoroborate (BMIM+BF4−) in poly(vinylpyrrolidone) (PVP)/AgCF3SO3/Al(NO3)3 complex membrane for enhancement of propylene/propane separation performance was investigated. When BMIM+BF4− was incorporated into PVP/AgCF3SO3/Al(NO3)3 complex membrane, the selectivity of propylene/propane mixture increased from 5 to 9 without diminishment of mixed-gas permeance. Furthermore, the PVP/AgCF3SO3/Al(NO3)3/BMIM+BF4− membrane exhibited long-term stability for more than 100 h, indicating that Ag+ ions were highly stabilized. The coordinative interactions of the PVP/AgCF3SO3/Al(NO3)3/BMIM+BF4− membrane were characterized and compared with a PVP/AgCF3SO3/Al(NO3)3 membrane by TGA, FT-IR, XPS, and FT-Raman. As results, FT-IR and XPS showed the electrostatic interaction between the BF4− anions and Ag+ ions led to weakening of the interaction between the Ag+ ions and the CO bond of PVP. FT-Raman showed ion aggregates were easily formed by the interactions between Al3+ and CF3SO3− in the PVP/AgCF3SO3/Al(NO3)3/BMIM+BF4− electrolyte membranes.