The Preparation And Gas Permeation Performance Of Comb-branched Copolymer SPEEK Grafted PEG

Increasing CO2 emissions in the environment have contributed to global warming and climate change,which are issues of great concern today.Therefore,its capture has been widely acknowledged as very important to regulate these emissions.Membrane separation is considered as an emerging technology,which has the potential to be more environmentally friendly and energy saving.Ethylene oxide(EO)units in the polymer has been concluded that it appear to be the most useful groups to achieve high CO2 selectivity.The polymer of poly(ethylene oxide)membranes containing numbers of EO groups have become the most potential materials for CO2 separation and garnered growing interest.It’s significant for CO2 separation to prepare polymer membranes with high content and continuity ether oxygen group.In this paper,the method of sulfonating polymer grafted PEG to prepare comb-branched copolymer grafted PEG was put forward to increase ether oxygen content and adjust ether oxygen content distribution,which was useful to improve the CO2 separation performance.Fist,Molecular dynamics(MD)and grand canonical Monte Carlo(GCMC)simulations are used to study the free volume,permeability and selectivity of gases in comb-branched copolymer grafted PEG(SPEEK-g-PEG).And the performances of SPEEK-g-PEG are compared with CO2 separation commercial Pebax? membrane with ethylene oxide(EO)units.The simulation results indicated that ethylene oxide(EO)units effectively promote the permeability and selectivity of the CO2 in SPEEK-g-PEG,and SPEEK-g-PEG and Pebax? exhibit similar gas penetration behaviors.However,the gas permeability and selectivity of materials are greatly depended on the structure formation of SPEEK-g-PEG and Pebax?.Pebax? shows higher gases permeability because of the block copolymer structure with a hard segment and PEG block as a soft segment.While comb-branched copolymer SPEEK-g-PEG shows higher CO2 selectivity with rigid main chain PEEK and soft side chain PEG.In conclusion,comb-branched copolymer grafted PEG can significantly improve the CO2 selectivity performance of membrane materials by regulating the distribution of the EO groups.Secondly,the experiment was researched according to the molecular simulation results.The SPEEK-g-PEG/PEG gas membrane was prepared successfully and the membrane separation performance was researched.The experimental results show that low molecular weight PEG is easy to blend and react with SPEEK,which is useful to improve the stability of membrane and CO2 separation performance.The increasing PEG200 in the membrane is beneficial to improve the CO2 permeance and selectivity.The CO2 permeance is 53 Barrer,CO2/N2 selectivity is up to 69 and CO2/CH4 selectivity is 19.3,when the content of PEG200 in the membrane is 60 wt.%.The selectivity of SPEEK-g-PEG/PEG membrane is higher than that of Pebax? with PEG200 blend membrane that the CO2/N2 selectivity is 47 and CO2/CH4 selectivity is 15.9.CO2/N2 and CO2/CH4 selectivity are increased with the stress increasing and decreased with the temperature increasing.The low temperature and high pressure are advantageous to the membrane separation performance.The composite membrane has good stability,because polymer has good affinity with the PP support layer,and the permeability of the CO2 changed little and the selectivity is increased at 20℃ and 0.35 MPa pressure testing 15 days.