Research On Supported Liquid Membrane Based On Binary Metal Chloride DES For The Separation Of Ethylene/Ethane

Ethylene is the basic raw material of petrochemical industry.The ethylene output is regarded as an important indicator for evaluating the development level of petrochemical industry in a country.In the production of ethylene,the product is often a mixture of olefin and alkane.Because of the similar physical and chemical properties of plefin and alkane with the same carbon number,using the traditional low-temperature distillation method suffers huge energy consumption and high investment of equipment.So it is very necessary to develop a new method of high efficiency,energy saving and economic separation for the development of petrochemical industry in our country.The method of membrane separation using supported liquid membrane has the advantages of simple preparation process,high selectivity,high permeation flux,and economical and energy saving.The membrane solution is made of depp eutectic solution?DES?which is composed entirely of ions.It has the characteristics of atomic economy,extremely low vapor pressure and designability.In this paper,Cu⁺based DES was used to separate ethylene/ethane mixture through the principle that Cu⁺can reversibly complexed with ethylene.Binary metal chloride deep eutectic solvents were first prepared by adding different metal chlorides into 1-butyl-3-methylimidazolium chloride?[BMIM]Cl?/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 the ethylene/ethane separation experiments.For the SLM based on 0.5[BMIM]Cl-CuCl-1/15ZnCl₂ 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 ESI-MS,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.This study provides a new idea for improving the selective separation performance of ethylene/ethane mixed gas by the Cu⁺carrier,and explores the mechanism to contribute to the development of the olefin/alkane membrane separation process.