CO2 ayırımı için karışık matrisli membranlarda (KMM) inorganik katkı maddesi olarak Titanyum-silikalit-1 (TS-1) kullanımı

Mixed matrix membranes (MMMs) play an important role in the field of gas separation as synergistic effects of polymers and inorganic fillers is expected to overcome the limitations of polymeric membranes. These composite membranes have been prepared by dispersing the inorganic fillers into the polymer matrix. Material selection for both polymer and filler is a key aspect in the development of successful MMMs. Titanium-Silicalite-1 (TS-1) is a crystalline zeotype material in which tetrahedral [TiO4] and [SiO4] units are arranged in a MFI structure. Owing to this structure TS-1 shows a three-dimensional system of channels having molecular dimension of 5.1-5.6 Å. TS-1 is widely known for its unique catalytic selectivity for industrial oxidation reactions due to the specific features of its Ti active sites; however the selective adsorption properties of TS-1 and its potential as inorganic filler in MMMs have not been investigated. Its shape selectivity, hydrophobic nature, and high thermal stability make TS-1 an attractive candidate for MMM applications. The objective of this work is to explore its potential for CO2/CH4 and CO2/N2 separation applications. This work focuses on the synthesis of MMMs based on TS-1 dispersed in two different polyimides. Commercially available Matrimid® 5218 and in-house synthesized 6FDA-DAM polyimides are chosen as polymer matrix due to their CO2 separation properties which also depend on MMM synthesis scheme and casting conditions. Matrimid® has relatively lower (3-8 Barrer) CO2 permeability whereas 6FDA-DAM exhibit much higher (25-840 Barrer) CO2 permeability. TS-1 samples with an average crystal size of 200-300 nm were synthesized by hydrothermal method and characterized by X-Ray Diffraction (XRD), Dynamic Light Scattering (DLS), Scanning Electron Microscopy (SEM), Accelerated Surface Area Porosimetry Analyser (ASAP) and Intelligent Gravimetric Analyzer (IGA). IGA results showed that CO2 adsorption on TS-1 was approximately four times more than that of N2 and two times more than that of CH4. The transport properties of MMMs are strongly dependent on the nanoscale morphology at the interfacial region between the polymer matrix and the filler surface. One type of morphology obtained at the interface is the formation of interfacial voids which hinder the success of MMMs. The method used to improve the interface morphology and the membrane fabrication protocol change depending on the filler/polymer combination. In this work, an amino silane coupling agent ((3-aminopropyl)triethoxysilane-APTES) as integral chain linker was used to overcome the compatibility problem between the polymer and TS-1. Modification with APTES was performed in three different solvents; toluene (TOL), tetrahydrofluron (THF), isopropanol (IPA). Different polarities an kinetic diameters of the solvents in the modification reaction performances were also investigated. The results shows that using IPA as a modification reaction solvent lead to less reduction in gas sorption due to pore blockage. MMMs were prepared using the APTES-modified TS-1 particles using various preparation conditions. TS1-APTES-TOL / Matrimid® and TS1-APTES-IPA / 6FDA-DAM exhibited good compatibility with the polymer phase without any observable void in the SEM analysis.The separation properties of the MMMs were characterized by pure and mixed gas permeability measurements. Single gas measurements supporting with Maxwell model predictions demonstrated that incorporating TS-1 zeolites into the polymer matrix only concluded as increase in permeability and slight change in the selectivity due to lack of molecular sieving properties of the MFI zeolites for the gas pairs of CO2/CH4 and CO2/N2. On the other hand, interesting results were obtained from mixed gas experiments compared the single gas measurements. Deteroriation of permeability and enhancement in the selectivity that transfer the releated MMMs beyond the upper bounds for specifically CO2/CH4 separation. This change may be attributed to difference sorption capacity of the TS-1 zeolites for different gases, thus competitive adsorption inside the pore of the TS-1 crystals.