Detailed study on propylene/propane separation by new cellulose acetate/polyethylene glycol/ZIF-8 ternary mixed matrix membrane

• CA/PEG/ZIF-8 ternary mixed matrix membranes prepared for C3H6/C3H8 separation. • FTIR, SEM, TGA, and DMTA confirm good polymer–filler compatibility. • 30 wt% ZIF-8 drastically increases propylene permeability and doubles selectivity. • Selectivity improves with pressure up to 10 bar without plasticization effect. Light olefin/paraffin separation is one of the most challenging operations in the petrochemical industry due to the similar physical properties of these gases. Mixed matrix membranes (MMMs) represent a subclass of membranes with advanced features. MMMs incorporating metal–organic frameworks (MOFs) combine the high gas separation performance of MOFs with the unique advantages of polymeric membranes, such as low cost and ease of synthesis. In this study, ZIF-8, a subclass of MOFs, was incorporated into PEG-modified cellulose acetate (CA). The resulting MMMs demonstrated high separation performance for propylene/propane. Fourier-transform infrared spectroscopy (FTIR), field-emission scanning electron microscopy (FE-SEM), thermogravimetric analysis (TGA), and dynamic mechanical thermal analysis (DMTA) were employed to characterize the MMMs. Gas separation measurements were conducted on MMMs with different ZIF-8 loadings to evaluate propylene/propane separation performance. The permeability of propylene increased more than that of propane in all MMMs, with the membrane containing 30 wt.% ZIF-8 exhibiting the best performance. Propylene permeability increased significantly from 0.91 Barrer (for the unloaded membrane) to 14.75 Barrer at 2 bar. Moreover, propylene/propane ideal selectivity improved from 3.21 to 6.35, representing an enhancement of 97.82%. Conversely, the permeability of both gases showed a decreasing trend as the pressure increased up to 10 bar. For the MMM containing 30 wt.% ZIF-8, propylene and propane permeability decreased from 14.75 and 2.32 Barrer at 2 bar to 14.66 and 1.97 Barrer at 10 bar, respectively. However, propylene/propane ideal selectivity increased from 6.35 at 2 bar to 7.44 at 10 bar indicating no plasticization.