(573a) Superior Propylene/Propane Separation Performances of Asymmetric Mixed-Matrix Membranes By in-Situ ZIF-8 Formation with an Additive

Separation of propylene from propane is one of the most energy-intensive separation processes due to the similarities in their physico-chemical properties[1]. Zeolitic-imidazolate framework-8 (ZIF-8), consisting of a zinc center tetrahedrally coordinated with 2-methylimidazolate linkers, is one of the most promising molecular sieve materials for propylene/propane separation. Recently, our group developed a novel one-step ZIF-8-based asymmetric MMM fabrication strategy, termed “PIMOF”, enabling rapid formation of asymmetric MMMs with relatively high ZIF-8 loadings. The as-prepared MMMs showed unprecedentedly high C₃H₆/C₃H₈ (C3) separation performance as compared to other propylene-selective MMMs reported so far with the C₃H₆ permeance of ~ 7.5 GPU and C₃H₆/C₃H₈ separation factor of ~ 107.

In this presentation, we plan to present a new strategy to further improve the C3 separation performances of asymmetric MMMs prepared by the PIMOF. The strategy is based on incorporation of an additive (sodium formate) that modifies the ZIF-8 filler formation inside the polymeric matrix. The C3 separation performances of the resulting MMMs with sodium formate showed the unprecedented C₃H₆/C₃H₈ separation factor of 222.5 ± 1.79 and the C₃H₆ permeance of 10.1 ± 0.4 GPU, surpassing even most of the high-quality polycrystalline ZIF-8 membranes reported so far. Sodium formate functions as a deprotonator, enhancing the nucleation rate and consequently forming much smaller filler particles inside polymer than those formed without sodium formate. These smaller filler particles led to stronger polymer-particle interaction, further restricting linker swing motion and thereby enhancing C3 separation performances.

Reference:

1. Sholl, D.S. and R.P. Lively, Seven chemical separations to change the world. Nature, 2016. 532(7600): p. 435-437.