Study On The Preparation Of Mixed Matrix Membrane And Its Gas Separation Performance Based On The Non-clogging Dispersed Phase

In recent years,gas membrane separation has developed into an independent chemical operation unit,and its core is still to develop membrane materials with high gas permeability and high selectivity.Among them,mixed matrix membranes prepared by introducing high-performance micro-nanoparticles as a dispersed phase into the polymer matrix have become one of the research hotspots in the field of membrane material development.Aiming at the problem that the polymer matrix phase in the mixed matrix membrane easily penetrates into the dispersed phase particles and blocks the micro-nanoparticle microchannels,so that the high-performance micro-nanoparticles cannot function well.In this study,starting from the membrane formation method of the mixed matrix membrane and the configuration of the dispersed phase particles,the methods of preventing the microchannels of the dispersed phase particles from being blocked were explored,and then prepared the advanced mixed matrix membrane material and the gas separation membrane.On the one hand,it started with the membrane-forming method,and used the idea of solidifying the polymer matrix first,and then solidifying the dispersed phase particles to prevent the polymer matrix phase from penetrating into the micro-nanoparticle microchannels in the conventional method.In this paper,the mixed matrix membrane with nitrogen-doped porous carbons（NDPC）as the dispersed phase and polymer of intrinsic microporosity（PIM）as the polymer matrix was prepared by one-step method.The effects of thermal treatment membrane formation temperature and NDPC contents on the performance of mixed matrix membrane were investigated.The results showed that NDPC had good compatibility with the polymer matrix and was uniformly dispersed in the mixed matrix membrane.When the NDPC contents were 2 wt.%and5 wt.%,the CO₂ permeability of the mixed matrix membrane was 9.35 times and 11.92times of that of the original membrane,respectively,and the selectivity of O₂/N₂ and CO₂/N₂ remains good.On the other hand,starting from the configuration of dispersed phase micro-nanoparticles,hollow nanoparticles（HNPs）with dense shells were prepared by the interfacial polymerization-microemulsion system method,and then were introduced into the poly（ether-block-amide）（Pebax）,polydimethylsiloxane（PDMS）,PIM,polyetherimide（PEI）to prepare mixed matrix membrane,HNPs/Pebax,HNPs/PDMS,HNPs/PIM,HNPs/PEI.The effects of the type and content of hollow nanoparticles on the performance of mixed matrix membranes were investigated.The results showed that the polymer matrix and HNPs have good compatibility and uniform dispersion in the mixed matrix membrane.After incorporating them into the polymer matrix,the CO₂permeability of the mixed matrix membrane is 2.2 times of that of the original membrane when PIM-1 is used as the polymer matrix.The selectivity of O₂/N₂ and CO₂/N₂ remains good.Based on the performance and characters of the above mixed matrix membranes,the composite membranes with HNPs/PIM mixed matrix membrane as the selective skin layer and the polyacrylonitrile porous membrane as the support layer were prepared in this paper.The effect of pretreatment method and the pull-up speed on performance of the composite membrane were performed.The results showed that when the transition layer is added in the middle of the composite membrane and the pull-up speed is 1 m/min,the composite membrane maintains the self-supporting membrane selectivity,and the permeance of CO₂ can reach 4000 GPU,which has great application potential.