Crosslinkable mixed matrix membranes with surface modified molecular sieves for natural gas purification: I. Preparation and experimental results

Dense film mixed matrix membranes (MMMs) comprised of SSZ-13 dispersed in a crosslinkable polyimide (PDMC) were fabricated and evaluated for carbon dioxide/methane separations. MMMs containing 25% (w/w) as-received (AR) SSZ-13 exhibited a carbon dioxide permeability of 153 Barrers with a carbon dioxide/methane ideal selectivity of 34.7 at 65 psia and 35 °C. This represents a permeability enhancement of 129% and a decline in selectivity of 4.7% over neat PDMC (PCO2=66.9PCO2=66.9 Barrers, αCO2/CH4=36.4αCO2/CH4=36.4). A sieve surface modification procedure was developed with the aim of improving SSZ-13/PDMC MMM transport properties. MMMs containing 25% (w/w) surface modified (SM) SSZ-13 exhibited a carbon dioxide permeability of 148 Barrers and carbon dioxide/methane selectivity of 38.9 at 65 psia and 35 °C, representing enhancements in both permeability and selectivity of 121% and 6.9%, respectively. Mixed gas permeation analyses of MMMs containing SM-SSZ-13 using a 10% carbon dioxide/90% methane mixture shows that permeability and selectivity enhancements of 47% and 13%, respectively, over neat PDMC are possible at 700 psia and 35 °C.

► Analyses of untreated SSZ-13/PDMC membranes suggest interfacial defects.
► CO2/CH4 separation enhanced using reactively sized SSZ-13/PDMC membranes.
► PDMC membranes resistant to CO2-induced plasticization due to covalent crosslinks.