Mixed matrix membranes of aminosilanes grafted FAU/EMT zeolite and cross-linked polyimide for CO2/CH4 separation

Intergrowth Faujasite and EMC-2 zeolites (FAU/EMT) were grafted with 3-aminopropyltriethoxysilane (APTES), 3-aminopropylmethyldiethoxysilane (APMDES), and 3-aminopropyldimethylethoxysilane (APDMES) containing respectively trihydrolyzable ethoxy groups (3E), di-hydrolyzable ethoxy groups (2E), and monohydrolyzable ethoxy group (1E) in different polarities solvent of isopropanol (IPA), isopropanol/water mixture, 95/5 V/V (IPAW) and toluene (TOL) to prepare mixed matrix membranes with 6FDA-ODA polyimide cross-linked by APTMDS (Bis(3-aminopropyl)-tetramethyldisiloxane) as the organic phase. Membrane comprising amine-grafted zeolite with a commercial polyimide (Matrimid 5218 US) was also fabricated for comparison. The gas transport properties of these mixed matrix membranes (MMM) for pure gas and blends of CO2 and CH4 were investigated at 35 °C and 150 psi. The results showed that the performance of MMM with 6FDA-ODA at 25 wt.% zeolite is excellent for CO2/CH4 separation. A detailed study of the relation between MMM properties and their morphology as affected by their interactions with the amine-grafted inorganic phase and the cross-linking agent is reported.