Blending ZIF-67 into PDMS membranes to promote the separation performance of propylene/nitrogen mixed gas

The membrane-based gas separation is well-suited for the recovery of hydrocarbons from nitrogen-rich exhaust gases. However, the separation performance of the existing polymeric membranes was insufficient. In this study, zeolitic imidazolate framework-67 (ZIF-67) was synthesized and then incorporated into polydimethylsiloxane (PDMS) to prepare ZIF-67/PDMS mixed matrix membranes via the spin-coating method. The resultant ZIF-67 and membranes were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscope. The C3H6/N2 (20:80 vol) mixed gas separation tests indicated that the ZIF-67/PDMS membranes achieved the higher C3H6/N2 separation factor but the lower C3H6 permeance in contrast with pure PDMS membrane. At the ZIF-67 loading of 5 wt%, the membrane displayed the optimal separation factor of 16.5 with comparable C3H6 permeance of 86.9 GPU. Besides, the relatively low operating temperature and pressure were advantageous to gaining good gas separation performance.