(645h) Modelling Hierarchical Carbon-Based Materials for CO2 Capture and Separation

Among the capture and separate CO₂ (CCS) from diluted sources, such as gases emitted from fossil fuel combustion and other industrial processes, adsorption with solid materials is emerging as a viable alternative to the traditional amine absorption process due to the improvement in energy efficiency and potential cost reductions [1]. Common materials that have been extensively studied as potential adsorbents for CO₂ capture from a flue gas include zeolites, silicas, polymeric resins, Metal-Organic Frameworks (MOFs) and carbon-based structures [2]. Carbon-based materials are very attractive for this endeavor due to their versatility, as do not require moisture removal (unlike most zeolites and some MOFs), their ability to present high CO₂ capacity depending on their preparation process, while being easy to regenerate and with excellent mechanical and chemical stability [3]. However, further knowledge is still needed about the effect of surface characteristics (e.g., pore size distribution, surface area, density and species of surface groups, etc.) and the topological nature of the connected pore structures on the phase changes for the confined fluids for their optimization for final use.

The work presented in this contribution combines molecular and process modelling for developing efficient, low-cost adsorbent materials for carbon dioxide capture, aiming at using the fundamental understanding of the phenomena happening at the molecular level to optimize their performance under process conditions. Moreover, such molecular simulation methods can be used as a screening method at a very moderate computational expense to fine-tune the process needs, thus making an important contribution to the optimization of the swing adsorption process performance. We present and discuss results concerning two different carbon-based materials: zeolite-templated carbons (ZTCs) and activated carbon samples developed from seeds of date fruits (Phoenix dactylifera, AC-DS) from the United Arab Emirates [4]. Furthermore, the effect of the inclusion of hierarchical features, i.e., a collection of micro and mesopores, is analyzed in detail. We showcase the capabilities and limitations of a developed molecular simulation-based screening tool for the efficient removal of CO₂ from industrial gas streams –CO₂/N₂ and CO₂/CH₄, with and without including water traces as impurities- by adsorption at relevant gas separation process conditions. The modelling approach for the carbon-based solid sorbents, previously validated and systematically applied for other processes [4], consists of a collection of three-dimensional platelets, packed in random positions and orientations in a periodic simulation cell, with defects and oxygenated groups. Results presented include the adsorption of the pure components, the properties of both binary CO₂/N₂ and CO₂/CH₄ mixtures, and the effect of T,P,X conditions on the performance of pressure and temperature swing adsorption processes.

This work is funded by Khalifa University of Science and Technology under projects RC2-2019-007 and CIRA2018-103.

References

[1]. Rao, A.B., Rubin, E.S., Keith, D.W., Morgan, M.G. Energy Policy 34(18), 3765–3772 (2006).

[2]. Bahamon, D., Vega, L.F. Chem. Eng. J. 284, 438-447 (2016).

[3]. Rashidi, N.A., Yusup, S. J. CO₂ Util., 13, 1-16. (2016).

[4]. Bahamon, D., Ogungbenro, A.E., Khaleel, M., Abu-Zahra, M.R.M., Vega, L.F. Ind. Eng. Chem. Res., 59, 7161-7173 (2020).