REMOVAL OF GREENHOUSE GASES BY TERNARY COMPONENT POLYMERIC MEMBRANES

Date

2024-1-23

Author

Süzen, Betül Sena

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SF6, one of the fluorinated greenhouse gases such as hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and nitrogen trifluoride (NF3), is the most potent greenhouse gas identified so far. SF6 is used in the electronics industry in the production of semiconductors and as an insulation gas in electric power systems. Although the amount of SF6 used in the industry is low, it strongly influences climate change with its greenhouse gas effect, which is 23900 times more potent than CO2. A mixed matrix membrane is prepared by dispersing inorganic fillers throughout the polymer matrix to improve the performance of the polymer. Zeolites, carbon nanotubes, metal oxides, and metal-organic frameworks (MOFs) are widely used as filler materials to prepare mixed matrix membranes (MMMs). MOFs are a class of porous materials consisting of organic linkers joined to metal nodes to form a crystalline framework. MOFs are widely used in the preparation of MMMs due to their advantages, such as tunable pore size and high surface area. In this study, it is aimed to prepare mixed matrix membranes to separate SF6/N2 mixtures containing less than 10% SF6. Since the molecular size of SF6 (0.56 nm) is greater than N2 (0.36 nm), the membranes produced are aimed to be reverse-selective to SF6. PEBAX 1657 block copolymer was used to prepare dense polymeric membranes for the gas separation. PEBAX 1657 contains blocks of glassy, rigid polyamide segments (PA) (40%) and rubbery, flexible polyether segments (60%). To obtain SF6 selective membranes, the SF6/N2 sorption selectivity of membranes should be increased, and the fast diffusion of large SF6 through the membranes should be achieved. For this purpose, HKUST-1, which has a high sorption selectivity for SF6 over N2, was synthesized and added to the membrane matrix. Besides, ZIF-68, with a pore size of approximately 0.9 nm, was synthesized and introduced to the membranes to increase the diffusion rate. During membrane preparation, controlled filler distribution was studied to improve the gas separation effects of both fillers. The filler materials and membranes were characterized by XRD, SEM, N2 adsorption, and TGA. Besides, the single gas permeation rates N2, CO2, and SF6 were measured through membranes at 3 bar transmembrane pressure and 35oC in a system designed in our laboratory. Incorporating SF6 selective HKUST-1 into the polymer matrix enhanced the ideal selectivity of SF6/N2 three times compared to the pure membrane. The separation performance was thought to be improved even further for the mixed gas experiments due to competitive adsorption.

Subject Keywords

SF6 Separation, Mixed Matrix Membrane, MOF, PEBAX, Reverse Selective Membrane

URI

https://hdl.handle.net/11511/108339

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Graduate School of Natural and Applied Sciences, Thesis