Preparation And CO₂ Separation Of High-Performance SPEEK/Y Molecular Sieve Mixed Matrix Membranes

The excessive use of coal,oil,natural gas and other fossil energy has led to increasingly serious greenhouse effect,which directly affects the sustainable development of human society.Therefore,many countries in the world have actively proposed countermeasures.In order to solve this problem,CO₂ capture is particularly important.Common CO₂ capture methods include absorption,adsorption,low temperature distillation and membrane separation methods.Among them,membrane separation methods have many advantages such as environmental friendliness,high efficiency and low investment.As a new type of CO₂ capture technology,membrane separation technology has received extensive attention and research.In this paper,in order to prepare the high-performance mixed matrix membranes for CO₂ separation,sulfonated poly（ether ether ketone）（SPEEK）is used as the polymer matrix.Simultaneously,Na Y and modified Na Y are added to prepare mixed matrix membranes to explore the relation between structures and properties,respectively.The specific research contents are as follows:（1）In order to obtain the high-performance mixed matrix membranes,Na Y is directly incorporated into the SPEEK matrix to prepare the SPEEK/Na Y mixed matrix membranes.Infrared spectroscopy（FTIR）,X-ray diffraction（XRD）,X-ray small angle scattering（SAXS）and scanning electron microscopy（SEM）are used to characterize the mixed matrix membranes.The effects of water content,Na Y loading,feed gas pressure and temperature on the gas separation performance of mixed matrix membranes are investigated.Simultaneously,the gas separation performance and long-term stability are investigated under mixed gas conditions.FTIR results show that there is a hydrogen bond between SPEEK and Na Y.The good compatibility between SPEEK and Na Y can be proved by the SEM results.The SAXS results prove that the addition of Na Y will increase the polymer chain spacing.It is found that when the Na Y loading is 20 wt%,the gas separation performance is the best（CO₂ permeability is 765 Barrer,CO₂/N₂selectivity is 63）,surpassing the 2008 Robeson upper bound.After 360 h of operation,the CO₂ permeability and CO₂/N₂ selectivity are 730 Barrer and 58,respectively,which are still stable.This is mainly because Na Y is distributed uniformly in the membranes.At the same time,there is a strong hydrogen bond between SPEEK and Na Y,so that Na Y can better exert molecular sieving performance in the membranes.（2）In order to prepare the better gas separation performance mixed matrix membranes,K-Na Y-NH₂ with facilated-transport sieving hole is prepared,and then blends with SPEEK to prepare SPEEK/K-Na Y-NH₂ mixed matrix membranes for CO₂/N₂ separation.K-Na Y-NH₂ is characterized by FTIR,XRD and nitrogen adsorption.The effects of water content,K-Na Y-NH₂ loading,feed gas pressure and temperature on the gas separation performance of the mixed matrix membranes are investigated.The mixed gas separation performance and long-term stability are tested,too.The results show that the CO₂ permeability and CO₂/N₂ selectivity of SPEEK/K-Na Y-NH₂-20 mixed matrix membrane are 917Barrer and 82 at 1 bar and 25°C,respectively,far surpassing the 2008 Robeson upper bound.The main reason is that the specific surface area,pore volume and pore size of Na Y are reduced after modification,and the surface of Na Y has amino groups that promote CO₂ transport,which can effectively improve gas separation performance.Mixed gas tests are conducted on the mixed matrix membranes,and it is found that the gas separation performance in the mixed gas is slightly lower than that of pure gas,and it has good stability in 360 h,indicating that the prepared mixed matrix membranes has certain industrial application prospects.