AI Article Synopsis
- Propylene/propane separation is typically done through energy-heavy cryogenic distillation, but membrane-based methods could be more efficient.
- Despite potential benefits, existing polymeric membranes aren't suitable for commercial use due to their limitations.
- Researchers have developed ZIF-67 membranes that intergrow with ZIF-8, showing remarkable propylene/propane separation capabilities, achieving separation factors around 200 when enhanced with additional ZIF-8 layers.
Article Abstract
Propylene/propane separation is one of the most challenging separations, currently achieved by energy-intensive cryogenic distillation. Despite the great potential for energy-efficient membrane-based separations, no commercial membranes are currently available due to the limitations of current polymeric materials. Zeolitic imidazolate framework, ZIF-8, with the effective aperture size of ∼4.0 Å, has been shown to be very promising for propylene/propane separation. Despite the extensive research on ZIF-8 membranes, only a few reported ZIF-8 membranes have displayed good propylene/propane separation performances presumably due to the challenges of controlling the microstructures of polycrystalline membranes. Here we report the first well-intergrown membranes of ZIF-67 (Co-substituted ZIF-8) by heteroepitaxially growing ZIF-67 on ZIF-8 seed layers. The ZIF-67 membranes exhibited impressively high propylene/propane separation capabilities. Furthermore, when a tertiary growth of ZIF-8 layers was applied to heteroepitaxially grown ZIF-67 membranes, the membranes exhibited unprecedentedly high propylene/propane separation factors of ∼200 possibly due to enhanced grain boundary structure.
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| http://dx.doi.org/10.1021/jacs.5b06730 | DOI Listing |
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Article Synopsis
- Filler morphology control significantly improves gas separation in mixed matrix membranes (MMMs) through the design of a vertical transport channel utilizing crystal twinning in ZIF nanoplate.
- Twinned ZIF-8 (TZIF-8) enhances propylene/propane separation when added to 6FDA-DAM polymer, achieving a propylene permeability of 40 Barrer and selectivity of 82.
- The study indicates that the structure of the TZIF-8 provides effective pathways for desired gas molecules while creating barriers for undesired ones, outperforming previous MMMs and matching polycrystalline ZIF-8 membranes.
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