Preparation And Gas Separation Performance Of Mixed Matrix Membranes Of Polyimide And Porous Fillers

Gas separation membranes generally can be divided into two types, organic polymers and inorganic molecular sieves membranes. Because organic polymer membranes usually have low selectivity, while inorganic molecular sieves membranes are brickle, the latest mixed matrix membranes (MMMs), consisting of inorganic porous fillers into polymer matrix, will be the promising potential for future applications.polyimide(PI) is a kind of important membrane material because of its excellent gas selectivity and mechanical properties, it has been applied to industrial production. However, for the polymeric materials, a rather general upper limit exists between permeability and selectivity, i.e., a membrane with high selectivity tends to have low permeability; and visevers. Metal Organic Frameworks (MOFs) is a kind of new multi-porous materials, with adjustable pore volume, surface and chemical properties. With MOFs dispersing into polyimide matrix, PI/MOF MMMs provided the evidence that MMMs is an efficient membrane approach for gas separation.In this paper, based on a survey of the development, performance and synthesis of polyimide and metal organic framework, the intrinsic PI asymmetric membrane and PI/MOFs, PI/MCM-41and PI/SiO2asymmetric MMMs were systematically investigated.Firstly, pyromellitic (PMDA) and oxydianiline (ODA) were selected as monomers to fabricate intrinsic PI asymmetric membranes through the programmed-temperature imidation. The influence of membrane preparation conditions, such as the bath temperature, membrane thickness and membrane repair layer were studied.Secondly, three different types of MOFs of Cu3(BTC)2, MOF-5and MIL-53(Al) were synthesized and characterized by XRD, BET and TG etc. Thirdly, different fillers of MOFs, MCM-41and SiO2were dispersed into PI matrix to fabricate a series of PI/filler asymmetric MMMs. The membrane structures were characterized to investigate influences of the pore size and the surface properties on the gas separation. The gas permeability of pure H2、He、CH4、N2and CO2were measured.The results showed that the pore size and the surface properties of doping particles influence the Separation properties of membranes.The separation properties of asymmetric polyimide membranes is far higher than current membranes.The separation properties of PI/Cu3(BTC)2and PI/MIL-53(Al) mixed matrix membrane is higher than pure polyimide membranes,The separation properties of other mixed matrix membrane is lower than pure polyimide membranes.Through the contrast of separation properties of PI/MOFs (microprous),PI/SiO2(without porous) and PI/MCM-41(mesoporous),Reveal the mechanism of improve separation properties effectively through filling MOFs to PI.