303794 Preparation and Gas Separation Properties of Polyetherimide(PEI)/ZIFs Nanocomposite Membranes
The use of membranes to selectively remove CO2 from mixtures is of interest for a wide variety of applications such as upgrading of natural gas, landfill gas recovery, enhanced oil recovery and global warming prevention . However, one of the major problems confronting the use of membrane-based CO2 separation technology is the lack of membranes with both high permeability and high selectivity. Today, much of the research work is being addressed to the investigation of new materials and to the development of new membrane structures that exhibit both higher selectivity and permeability to specific gases. Recently, metal organic frameworks (MOFs) are used as the filler for MMMs, and several reports showed positive results [2, 3]. Good wetting properties between the two phases can be expected because of the organic moiety of the MOFs. Besides, MOFs can provide nearly unlimited porous structures and compositions, while only a small number of zeolite types are successfully applied in MMMs. Among numerous MOFs, zeolitic imidazole frameworks (ZIFs) draw lots of attention due to their superior chemical and thermal stability. They are very promising materials for several important applications, such as gas storage, chemical sensor, and separation process. Furthermore, several ZIFs can be synthesized easily and fast at low cost, such as ZIF-8 and ZIF-7 [4, 5]. In recent years, several researchers have incorporated ZIF-8 and ZIF-7 particles into polymeric membranes to form MMMs for gas separation. The as-prepared ZIF membranes not only improve gas separation but also make large strides toward industrial applications. ZIFs with sodalite topology, such as ZIF-7, ZIF-8, ZIF-9, and ZIF-90, are of particular interests for membrane applications, due to their monomodal pore size distributions and special diffusion pathways for guest molecules, i.e. large sodalite cages interconnected by small six-membered rings, resulting in an uncoupled flux of the molecular components in a mixture separation .
In this study, the preparation of polyetherimide (PEI)/ZIF-7 and polyetherimide (PEI)/ZIF-8 nanocomposite membranes were studied in different nanoparticles compositions. The morphologies and gas separation properties were determined for all membranes. Within the context of this study, the effects of nanoparticles that contain the different hydrophobic surface groups on the membrane morphologies and gas permeabilities were investigated. The membrane morphologies were observed by the scanning electron microscopy (SEM). Thermal properties of membranes were determined by thermogravimetric analyses (TGA).The gas permeabilities of PEI/ ZIF-7 and PEI/ ZIF-8 nanocomposite membranes were measured for H2, CH4 and CO2 pure gases at 35ºC and the selectivities of all membranes were calculated.
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