A Novel Supported Liquid Membrane Based on Binary Metal Chloride Deep Eutectic Solvents for Ethylene/Ethane Separation

Binary metal chloride deep eutectic solvents (DESs) were first prepared by adding different metal chlorides into 1-butyl-3-methylimidazolium chloride ([BMIM] CO/CuCl DESs to improve the activity of the Cu+ carrier for ethylene/ethane separation. The binary metal chloride DESs were impregnated in the polyvinylidene fluoride microporous membrane to prepare the supported liquid membranes (SLMs). The performance of the SLMs based on binary metal chloride DESs was evaluated by ethylene/ethane separation experiments. For the SLM based on 0.5[BMIM]Cl-CuCl-1/15ZnCl(2) DES, the selectivity of ethylene/ethane mixture increased from 10.7 to 17.8, and the ethylene permeability decreased slightly from 28.6 barrer to 25.8 barrer, compared to 0.5[BMIM][Cl] SLM without ZnCl2. Furthermore, it exhibited long-term stability for more than 150 h. The beneficial role of ZnCl2 for Cu+ carrier was analyzed by electrospray ionization mass spectrometry, Raman spectroscopy, and quantum mechanical calculation. The Raman spectrum showed that the Cu-Cl bond was weakened with the addition of ZnCl2. Quantum mechanical calculation revealed that the electron transferred from a Cl- ion of CuCl2- to the Zn2+ ion, which led to the weakening of the Cu-Cl bond and the activation of the Cu+ carrier.