(347f) Efficient Separation of Olefin and Paraffin Using Anion-Pillared Metal-Organic Frameworks

Olefin/paraffin separation is a momentous and challenging process for the production of polymer-grade C₂H₄ and polymer-grade C₃H₆ with high energy penalty. In 2016, about 0.3% global energy was used to purify C₂H₄ and C₃H₆. However, similar molecular size and physical properties of olefin/paraffin lead to great challenge for the separation of C₂H₄/C₂H₆ and C₃H₆/C₃H₈, which usually realized by energy-extensive cryogenic distillation. Metal organic frameworks (MOFs) and mixed matrix membranes (MMMs) are promising approaches for gas purification, while it is still very rare for energy-efficient materials without side effects to overcome the trade-off phenomenon (between selectivity and uptake capacity or between selectivity and permeability).^1,2,3 In the presentation, we will discuss strategies trying to address the problem mentioned above and recent advances of our group in the context of C₂H₄ and C₃H₆ purification. Firstly, we report the separation of C₃H₆ and C₃H₈ with two isostructural anion-pillared metal-organic frameworks (GeFSIX-2-Cu-i (also termed as ZU-32) and SIFSIX-2-Cu-i). Interestingly, GeFSIX-2-Cu-i shows a high uptake ratio of C₃H₆/C₃H₈, outperforming most of the existing materials. Furthermore, the breakthrough experiments for C₃H₆/C₃H₈ (50/50, v/v) binary mixtures were performed on GeFSIX-2-Cu-i and SIFSIX-2-Cu-i, respectively, which exhibits good dynamic separation and recyclability. The binding sites of GeFSIX-2-Cu-i for C₃H₆ and C₃H₈ were investigated by the first-principles density functional theory (DFT) calculations to give insights into the interaction mechanisms. After that, we incorporated SIFSIX-2-Cu-i in 6FDA-DAM polyimide to create MMMs for the separation of C₂H₄/C₂H₆ and C₃H₆/C₃H₈. Gas permeation experiments showed that the permeabilities of C₂H₄ and C₃H₆ as well as the selectivities of C₂H₄/C₂H₆ and C₃H₆/C₃H₈ have increased significantly compared with pure 6FDA-DAM membrane. Our work indicates that the anion-pillared metal organic frameworks can be considered as excellent candidates for the separation of olefin/paraffin purification.

Acknowledgement:

This work was supported by the National Natural Science Foundation of China (Grant No. 21725603, 21938011, and U1862110), the National Program for Support of Top-notch Young Professionals (H.X.), and the Research Computing Center in College of Chemical and Biological Engineering at Zhejiang University.

References:

1. Cui XL, Chen KJ, Xing HB, et al. Pore chemistry and size control in hybrid porous materials for acetylene capture from ethylene. Science. 2016; 353(6295): 141-144.
2. Zhang ZQ, Yang QW, Cui XL, et al.Sorting of C4 Olefins with Interpenetrated Hybrid Ultramicroporous Materials by Combining Molecular Recognition and Size-Sieving. Angewandte Chemie-International Edition. 2017; 56 (51): 16282-16287.
3. Wang XB, Zhang PX, Zhang ZQ, et al.Efficient Separation of Propene and Propane Using Anion-Pillared Metal-Organic Frameworks. Industrial & Engineering Chemistry Research. 2020; 59 (8): 3531-3537.