A polyimide/poly( N -vinylimidazole) membrane for CO 2 /CH 4 separation with high selectivity and permeability

Membranes with both good permeation and selectivity are highly desired for gas separations. In this study, we synthesized a new 6FDA-type polyimide copolymer 6FDA-BDTA-ODA, and then an organic polymer of poly ( N-vinylimidazole) was doped into the polyimide to prepare mixed matrix membranes (MMMs). We also studied the effect of poly ( N-vinylimidazole) contents on the separation performance of MMMs. The results showed that the ideal selectivity for CO 2 /CH 4 was improved by adding the poly ( N-vinylimidazole) filler. The ideal selectivity reached 63.5 with 6 wt% poly ( N-vinylimidazole) loading with the permeability of 29.2 Barrer. The highly permeable MMMs showed a considerably enhanced performance for CO 2 /CH 4 that close to the 2008 Robeson upper-bound. The gas separation performance of the prepared MMMs for CO 2 /CH 4 was improved compared to that of the pure polymer membrane, indicating that the copolyimide/poly ( N-vinylimidazole) MMMs have promising applications in CO 2 /CH 4 gas separation.