Enhanced CO2 permeability in Matrimid® 5218 mixed matrix membranes for separating binary CO2/CH4 mixtures

Membrane gas separation is an emerging technology used for the separation of CO2. Matrimid® 5218, one of the current polymers used in membrane gas separation, has good selectivity, but poor CO2 permeability. We wondered if its CO2 permeability could be enhanced by the addition of a CO2-philic additive (PEG 200) and ZIF-8 nanoparticles. ZIF-8 particles were synthesized with a nanoparticle size of 33.83 ± 6.2 nm. These particles were characterized by SEM and XRD. Dense film-casting method was used to prepare novel ternary mixed matrix membranes with low PEG concentrations (4 wt%) at different filler loadings (10-40 wt%). In CO2/CH4 binary mixtures, binary and ternary MMMs membranes were tested at fixed feed composition (50:50) and different feed pressures (from 2 to 8 bar). The MMMs were also characterized using SEM, EDX, DSC, and TGA. Finally, the incorporation of 30 wt% of ZIF-8 nanoparticles leads to increase the CO2 permeability in binary (up to 31.47 Barrer) and ternary MMMs (up to 33.12 Barrer); pointing out that the addition of PEG and ZIF-8 enhanced the CO2 permeability in the neat Matrimid® membranes (7.16 Barrer). Our results suggest that such ternary MMMs have considerable potential for use in CO2 separation applications.