Customized facilitated transport membranes by mixed strategy for ethylene/ethane separation

Abstract Mixed strategy has been widely utilized to design novel membranes or tailor membrane structure, however the construction of facilitated transport membranes (FTMs) with mixed strategy has rarely been reported. In this work, eight kinds of mixed protic ionic liquid (MPIL) derived FTMs (MPIL-FTMs) were designed with mixed strategy for highly efficient ethylene/ethane separation by impregnating MPILs and ethylene transport carrier into porous support. The morphology of MPIL-FTMs were characterized by SEM and AFM, and their molecular interactions were investigated by 1H NMR, FTIR and DSC. The MPIL-FTMs exhibited long-term stability and various ethylene permeability-ethylene/ethane selectivity combinations, which indicated mixed strategy could easily customize the separation performances of MPIL-FTMs. Moreover, a fundamental law for mixed strategy was obtained that the two parent PILs with similar chemical structure and molecular interactions favored the synchronous improvement of C2H4 permeability and C2H4/C2H6 selectivity. For example, the C2H4 permeability of the [BA][Pyr][NO3] derived MPIL-FTM reached up to 561.0 Barrer with improved C2H4/C2H6 selectivity of 26.7, which were superior to most of reported membranes, thus breaking through the ubiquitous trade-off effect. This study proves the mixed strategy is a promising platform for the design of high-performance FTMs as well as their structure modification, and the marriage of mixed strategy with diversity of ILs creates enormous opportunities to construct advanced membranes for energy-intensive gas separations.