Intrinsically Microporous Ladder Polymer-based Carbon Molecular Sieve Membranes for Gas Separation Applications
KAUST DepartmentPhysical Science and Engineering (PSE) Division
Embargo End Date2023-04-27
Permanent link to this recordhttp://hdl.handle.net/10754/676614
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Access RestrictionsAt the time of archiving, the student author of this dissertation opted to temporarily restrict access to it. The full text of this dissertation will become available to the public after the expiration of the embargo on 2023-04-27.
AbstractIndustrial separations – primarily dominated by thermally driven distillation-based processes – consume 10-15% of the global energy production and emit more than 100 million tonnes of CO2 annually. Membrane technology, a 90% thermodynamically more energy-efficient than distillation processes, could be a desirable alternative with potentially lower energy consumption and lower carbon footprint. Industrial implementation of membrane technology, particularly for olefin/paraffin separations and hydrogen purification from syngas, remains challenging due to the substantially low mixed-gas selectivity of the currently available polymeric materials. Carbon molecular sieve (CMS) membranes – formed by high-temperature pyrolysis of solution-processable polymeric-based precursors at an oxygen-free atmosphere – have shown superior gas separation performance far beyond the polymeric upper bounds for many gas-pairs (e.g., CO2/CH4, N2/CH4). The ultimate goal of the research reported in this dissertation was to develop highly performing CMS membranes for industrially important but challenging gas separation applications (e.g., C2H4/C2H6, H2/CO2, etc.). This work successfully introduced a promising approach to fine-tune the pore size distribution of CMS membranes through a systematic modification of the contortion sites of highly aromatic ladder polymer of intrinsic microporosity (PIM) precursors. CMS membranes derived from Trip(Me2)-TB – a precursor with large and thermally stable triptycene units – demonstrated unprecedented pure- and-mixed C2H4/C2H6 selectivities of 96 and 57, respectively, with relatively higher ethylene permeability than other CMS membranes. Similarly, CMS membranes derived from an alternative ladder PIM-based precursor, EA(Me2)-TB, also showed an outstanding performance for C2H4/C2H6 with a pure-gas selectivity up to 77 but with, however, low ethylene permeability of 0.35 barrer. Furthermore, CMS membranes derived from ladder CANAL-TB-1 – a precursor with the smallest contortion site – exhibited superior pure- and-mixed H2/CO2 selectivities of 248 and 174, respectively, due to their tightly packed structure enabled by the lack of any shape-persistence unit such as triptycene. CMS membranes fabricated in this work also showed promising gas separation performance for many other important energy-intensive industrial applications, including CO2/CH4, O2/N2, N2/CH4, H2/CH4, etc. In summary, this dissertation frameworks a facile and effective approach to obtain CMS membranes with exceptional gas separation performance by rational design of the contortion sites of intrinsically microporous ladder polymer-based precursors.
CitationHazazi, K. (2022). Intrinsically Microporous Ladder Polymer-based Carbon Molecular Sieve Membranes for Gas Separation Applications. KAUST Research Repository. https://doi.org/10.25781/KAUST-550I3