Construction Of Carrier-facilitated Transport Membrane With Tunable Nanochannels For Highly Efficient Ethylene/ethane Separation

Olefin/paraffin separation is one of the most important separation processes in chemical industry,which is mainly accomplished by the energy-intensive cryogenic distillation.The implementation of membrane technology to replace or combine with energy-intensive cryogenic distillation for precise separation of ethylene/ethane mixture proves an extremely important yet highly challenging task.Inspired by the hierarchical structure and facilitated gas transport of biological membranes,highly selective ethylene/ethane separation membranes are fabricated by an impressive strategy combined nanochannels with carrier-facilitated transport,which accomplishs the energy-saving and efficient separation of ethylene/ethane.The main findings are as follows.The fabrication of protic ionic liquid(PILs)based carrier-facilitated transport membranes with nanochannels and the investigation of its perofrmances for ethylene/ethane separation:PILs were utilized for the fabrication of carrier-facilitated transport membranes containing silver salt as the ethylene transport carrier to perform ethylene/ethane separation.The intrinsic nanostructures of PILs were adopted to construct fast and selective ethylene transport nanochannels.The investigation of structure-performance relationships of carrier-facilitated transport membranes suggested that transport nanochannels(polar domains of PILs)could be tuned by the sizes of cations,which greatly manipulated activity of the carrier and determined the separation performances of membranes.Morover,the presence of ether group and hydroxyl group in PILs significantly enhanced the ethylene/etahne selectivity.The fabrication of deep eutectic solvent(DESs)based carrier-facilitated transport membranes with nanochannels and the investigation of its perofrmances for ethylene/ethane separation:a series of deep eutectic solvents(DESs)containing NO₃^-as anion were designed,synthesized and characterized for the first time.Then,novel Ag/DES-FTMs were fabricated successfully through the incorporation of the transport carrier(Ag NO₃)into as-synthesized DESs.The resuts of spectral characterizations and ethylene/ethane separation performances of Ag/DES-FTMs suggested that the regulation of hydrogen bonding,electrostatic and coordinative interactions between DES and carrier by optimizing the HBAs,HBDs and their molar ratios,could tune the intrinsic nanostructure of Ag/DES-FTMs and be conducive to constructing interpenetrating and continuous apolar domains and polar domains,which could efficiently promote the disassociation of carrier and increase the interaction between carrier and ethylene,leading to high ethylene permeability and ethylene/ethane selectivity.The fabrication of bioinspired graphene oxide membranes with nanochannels and the investigation of its perofrmances for ethylene/ethane separation:a highly selective ethylene/ethane separation membrane is explored through the fixation of a silver ion carrier and the impregnation of ionic liquid within 2D nanochannels of graphene oxide laminate,where plenty of ethylene-permeating in-plane nano-wrinkles and ethylene-facilitated plane-to-plane nanochannels were constructed.By virtue of synergistic effects of molecular sieving and carrier-facilitated transport,an unprecedented combination of high ethylene permeance(72.5 GPU)and superhigh ethylene/ethane selectivity(215)was achieved,out-performing currently reported advanced membranes.Moreover,molecular dynamics simulations verified a favorable membrane nanostructure for fast and selective transport of ethylene molecules.The fabrication of boron nitride membranes with nanochannels and the investigation of its perofrmances for ethylene/ethane separation:A BN membrane with a distinct nanoconfinement effect toward efficient ethylene/ethane separation was presented.The horizontal and inclined self-assembly of 2D BN nanosheets endowed the BN membrane with abundant percolating nanochannels,and these nanochannels were further decorated by reactive ionic liquids(RILs)to tailor their sizes as well as to achieve nanoconfinement effect.The noncovalent interactions between RIL and BN nanosheets favored the ordered alignment of the cations and anions of RIL within BN nanochannels,which contributed to a fast and selective ethylene transport.The resultant membranes exhibited an unprecedented separation performance with superhigh ethylene permeance of 138 GPU and ethylene/ethane selectivity of 128 as well as remarkably improved long-term stability for 180 h,outperforming reported state-of-the-art membranes.