In industry, ethylene (C 2 H 4 )/propylene (C 3 H 6 ) separations are usually performed by a cryogenic process, which is energy intensive. Membrane separation technology is an alternative separation process that saves energy and is efficient. In this study, blend membranes were prepared by doping polyethylene glycol (PEG600) into a poly(ether-block-amide) (Pebax® 2533) matrix and were used to separate the C 2 H 4 /C 3 H 6 mixture. The PEG 600 and Pebax® 2533 polymers have good compatibility because they share hydrogen bonds. The addition of PEG600 is conducive to the hydrophilicity and the free volume of blend membranes, and it is also conducive to the solubility of C 2 H 4 and C 3 H 6 in the membranes, which improves the ability of the membranes to separate this gas pair. The Pebax® 2533/PEG600 blend membrane with 15% (mass) PEG600 showed the highest separation performance in our investigated membranes, with a C 3 H 6 /C 2 H 4 selectivity of 8.9 and a C 3 H 6 permeability of 196 barrer (1 barrer = 1.33 × 10 14 m 3 (STP)·m·m −2 ·s −1 ·kPa −1 ) at 238 K and 0.2 MPa, which is higher than that of the Pebax® 2533/NaY-6% (mass) membrane ( α C 3 H 6 /C 2 H 4 =6.5, P C 3 H 6 =211 barrer) reported in our previous work. It is confirmed that incorporating PEG600 into the Pebax® 2533 matrix to fabricate blend membranes is an efficient strategy for separating light olefins .
Jie Gao,Haizhuo Mao,Hua Jin,Chen Chen,Armin Feldhoff,Yanshuo Li
Membrane-based separation technology has evolved as a competitive approach for CO 2 capture from flue gas (mainly N 2 ). To achieve high separation performance, three partially NH 2 -, OH- and CH 3 OH- functionalized mixed-linker-ZIF-7 were successfully synthesized, and incorporated into polyether-block-amide (Pebax® 2533) polymer to form mixed-matrix membranes (MMMs). As evidenced by the CO 2 adsorption isotherms , introducing functional groups in the ZIF-7 framework was indeed beneficial for CO 2 adsorption. All MMMs composed of ZIF-7-NH 2 , ZIF-7-OH and ZIF-7-CH 3 OH offered better CO 2 /N 2 separation performance than the parent ZIF-7-Pebax® 2533 membrane, suggesting the positive effect of functionalized ZIF-7 fillers on the gas separation performance. Among the three functionalized ZIF-7 based MMMs, the ZIF-7-OH-Pebax MMMs exhibited the best performance for CO 2 /N 2 separation, which might be ascribed to the highest adsorption selectivity of CO 2 over N 2 predicted by ideal adsorbed solution theory (IAST) for ZIF-7-OH fillers. The 14% ZIF-7-OH-Pebax MMM showed high CO 2 permeability of 273 Barrer and CO 2 /N 2 separation factor of 38, which increased by 60% and 145% as compared with the neat Pebax membrane. The strategy of preparing functionalized MOFs with strong affinity for CO 2 provides an effective method to develop MMMs for highly efficient CO 2 separation.
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