2025 AIChE Annual Meeting

(401ah) Elucidating the Catalytic Performance of Fe/Ru-Embedded Carbon Molecular Sieve (CMS) Membranes for Ammonia Synthesis

Authors

Oishi Sanyal, West Virginia University
Mihir Kulkarni, West Virginia University
Madelyn R. Ball, West Virginia University
The research pertaining to this oral presentation is focused on developing a metal-embedded carbon molecular sieve (CMS) based catalytic membrane reactor for sustainable ammonia (NH3) synthesis. This catalytic membrane is aimed at overcoming the thermodynamic limitations of NH3 synthesis via continuous removal of NH3. These membranes can thus reduce the energy consumption associated with NH3 synthesis, while simultaneously ensuring high NH3 yields. CMS membranes, synthesized via high temperature pyrolysis of polyimide precursors, have been demonstrated as high-performance gas separation membranes. In this work, specific metals such as Fe and Ru have been incorporated within the polyimide matrix prior to the pyrolysis process, resulting in metal-embedded CMS membranes. The embedded metal is designed to act as the catalytic site , while the CMS membrane itself will enable separation of NH3 from similar-sized H2 and N2 molecules. Primarily, Fe and Ru will be used as the metals, while a fluorinated-copolyimide will be used as the polymer precursor for CMS. A range of metal incorporation techniques and synthesis conditions will be analyzed, and the resulting materials will be characterized in terms of both separation and catalytic properties. The separation properties will be reported in terms of sorption coefficients for NH3, N2 and H2 and these results will also be used to elucidate the morphological structure of CMS. Specifically, a sorption-based method to investigate the structural changes to the CMS membranes, before and after exposure to high temperature H2, will be discussed. The reaction properties, on the other hand, will be reported in terms of steady-state NH3production using these metal-embedded CMS membranes. Results comparing the metal containing CMS membranes with a traditional activated carbon supported catalyst containing the same metal, will be presented in terms of NH3 yield per gm of metal. The metal content of both of these materials will be measured using Inductively coupled plasma mass spectrometry (ICP-MS). In addition, the metal-CMS membranes prepared via different synthesis protocols will also be compared, and the results will be reported in this oral presentation. The metal dispersion in case of these varied synthesis protocols will be quantified and for protocols which are speculated to lead to single metal (Fe or Ru) sites, corresponding single metal catalysts on conventional supports will be designed for comparison. Lastly, a range of characterization techniques such as X-ray diffraction, BET N2 and CO2 physisorption and Raman spectroscopy are being employed to complement the results from reaction and separation studies, and these results will also be highlighted in this talk.