Research On The Fabrication And Gas Separation Performance Of Poly(Ether-block-amide)Mixed Matrix Membrane

With the rapid development of social economy,the demand for energy and resources is increasing.However,the consumption of fossil fuels produces large proportion of greenhouse gas emissions,serious greenhouse effect and a series of ecological deterioration phenomena.Therefore,it has become an urgent issue to develop efficient greenhouse gas capture and storage technology?such as membrane separation technology?.Membrane separation technologies are identified as one of the most important gas separation technologies in the 21^stt century.Membrane materials are the core of the technology,of which the characteristics directly determine the separation efficiency and application prospects.However,conventional organic polymer membranes are limited to their own characteristics with little room to improve the properties.Therefore,inorganic substances different from the membrane matrix are introduced as disperse phase,to construct mixed matrix membranes?MMMs?so as to combine the joint advantages of organic and inorganic materials.However,in the preparation of MMMs,it is often found that the poor compatibility between organic and inorganic phases,resulting into the issues of hard membrane forming and poor separation performance.In this regard,five kinds of MMMs were developed for CO₂ separation by modification with two types of organic and inorganic dopants.The present work would lay a good theoretical and practical foundation for enriching membrane preparation,modification and commercial application.First,a series of MMMs were successfully developed via solvent evaporation method by using Pebax1657 as polymer matrix,and inorganic substances?NaY zeolite and SAPO-23zeolite?or organic substances?PEG-600 and PEG-400?as single dopant or organic-inorganic two component dopant.The thermal stability,microstructure and micromorphology,evolution of surface functional groups of membranes were analyzed by the techniques of thermogravimetric analysis,scanning electron microscopy and x-ray diffraction,Fourier transform infrared spectroscopy.The effects of preparation conditions such as type and amount of additive,permeation temperature,permeation pressure on the microstructure,micromorphology and separation performance of MMMs were investigated.Results have showed that:?1?The introduction of zeolite significantly reduces the crystallinity of the mixed matrix membranes,increases the distance between polymer molecular chains,in addition to the adsorption contribution from zeolite to CO₂ and improves the CO₂ permeability and CO₂/N₂ selectivity of MMMs.The MMMs made by 40wt%NaY zeolite show significantly an increased CO₂ permeability?131.8Barrer?and CO₂/N₂ selectivity?178.1?by 13.2%and ten fold at feed pressures of 0.2MPa at 30?,the separation performance of which surpasses the 2008 Robeson upper bound.?2?The introduction of PEG additive containing the rich ether oxygen groups is attractive for CO₂.The as-prepared MMMs exhibit reduced the crystallinity,increased distance between polymer molecular chains,and obviously improved gas separation performance.When the PEG-600 amount is 20wt%,the CO₂ permeability and CO₂/N₂ selectivity of MMMs are respectively 124.3Barrer and 115.8 under 30?and 0.25MPa.The separation performance of MMMs surpasses the 2008 Robeson upper bound.?3?With the binary component introduction of NaY zeolite and PEG-600,the efficiency is much higher than that of single doping component for regulating membrane structure,which not only improves the interfacial compatibility between polymer matrix and NaY zeolite and but also opens up new high-speed permeation channels.At feed pressures of 0.15MPa at 30?,the CO₂ permeability and CO₂/N₂selectivity of MMMs could respectively reach to 172.6Barrer and 107.9 which are made by20wt%PEG-600 loading and 30wt%NaY loading.In addition,the O₂ permeability and O₂/N₂selectivity of MMMs could respectively reach to 5.2Barrer and 7.8.Furthermore,the MMMs exceed the 2008 Robeson upper bound and is close to the commercial attractive area,which significantly improves the commercial value and application potential.