With the rapid development of the world industrial economy,the increase in demand for fossil energy leads to an increase in global CO2 emissions year by year.As the main component of greenhouse gases,CO2 has caused a series of serious problems,such as global climate warming,glacier melting,land desertification,and so on,which would threaten the survival of human beings and the sustainable development of society,has attracted widespread attention.Membrane separation technology is favored by researchers because of its advantages of high efficiency,sustainability,environmental protection,and so on.The carbon molecular sieve membranes have unique advantages of high temperature resistance,organic solvent resistance,acid and alkali resistance,etc,and it is superior to polymer membranes in CO2 gas separation performance.In this paper,pyromellitic anhydride-4,4’-diaminodiphenyl ethertype(PMDA-ODA)polyamic acid is used as a precursor of carbon molecular sieve membranes,and then mixed with porous material or porous carbon material.After that,the mixed matrix carbon molecular sieve membranes(CMSMs)with high separation performance were prepared by carbonization at 650°C.The doping of porous structure can effectively regulate the pore structure of the carbon molecular sieve membranes,and achieve efficient separation of CO2.The specific research contents and conclusions are as follows:(1)Firstly,the zeolite-like imidazole framework material ZIF-8 was prepared,and then was added to the PMDA-ODA polyamic acid solution to prepare the PMDA-ODA/ZIF-8 mixed matrix polymer membranes,and then the mixed matrix carbon molecular sieve membranses were obtained.TG-FTIR,FTIR,XRD,N2 and CO2 adsorption-desorption curves were used to characterize the PMDA-ODA/ZIF-8 CMSMs.The effects of pyrolysis temperature,thermal soak time,ZIF-8 loading and different inorganic fillers on the gas separation performance of the membrane were mainly studied;the permeability of the membrane to gas molecules with different kinetic diameters was explored;the membrane aging performance and mixed gas separation performance were studied.TG-FTIR results show that the membrane would release CO2,CO,CH4and H2O during pyrolysis,which could increase the porosity of the carbon molecular sieve membranes.The CO2 adsorption curve evaluates the membrane structure and porosity,proving that the PMDA-ODA/ZIF-8 CMSMs has 3.5?ultramicropores.XRD patterns indicate that the carbon molecular sieve membranes transform from amorphous carbon to graphite carbon.At 25°C and1 bar,the CO2 permeability and CO2/N2 selectivity of PMDA-ODA/ZIF-8CMSMs are 263.9 and 219 respectively,when the pyrolysis temperature is650°C,the thermal soak time is 1 h,and the ZIF-8 loading is 7 wt%,exceeding the Robeson upper bound.In the 120-day aging performance test,the selectivity of CO2/N2 for 100 day is as high as 248.(2)Hierarchical porous carbon(HPC)based on sodium lignin sulfonate was prepared,and then doped into PMDA-ODA type polyamic acid solution to prepare PMDA-ODA/HPC mixed matrix precursor membrane,then the PMDA-ODA/HPC CMSMs were obtained after high temperature carbonization.The HPC was characterized using nitrogen adsorption.The effects of the reaction temperature and reaction time of the HPC gel-like precursor,the activation time,activation temperature and KOH content of the carbon material,and the loading of HPC on the gas separation performance of the membrane were mainly studied.The effect of the membrane on gas molecules with different kinetic diameters was studied.The aging performance and mixed gas separation performance of the membrane were studied.The results show that the CO2 permeability and CO2/N2 selectivity of PMDA-ODA/CMSM loaded 5 wt%HPC are 864.5 Barrer and 100 respectively,when the reaction temperature and reaction time of the gel-like precursor are 160°C and 8 h;the activation time and activation temperature are 2 h and 800°C,respectively,and the KOH content is 1 g.The separation performance far exceeded the Robeson upper bound.In the aging resistance test for up to 60 days,the selectivity of CO2/N2 is as high as 120 for 30 days. |