Mesoporous silicas functionalised with primary and tertiary amines were prepared and dosed with 13CO2 under dry and wet conditions and the structure of CO2 species formed was monitored by ssNMR. The work was complemented with computational studies, at the DFT level, in which several molecular models of amine-grafted silicas were explored, each presenting distinct intermolecular interactions arrangements. The applied method avoids the use of “slurries”, has performed previously in other studies found in the literature, allowing a detailed molecular-level understanding of the CO2 capture process, assessing the influence of a common contaminant – water – in the CO2 capture process (even in the presence of very small amounts ca. 0.7 kPa). Water is an important component of combustion gases, taking a decisive role in the CO2 speciation and as such, the studies performed in the scope of this project have allowed the team to achieve a better understanding of the structure of CO2 species formed in such materials under moist conditions, including their relative stability in the presence or absence of water. Furthermore, we have also introduced a third entity into the system by studying the CO2 adsorption in the presence of CH4, under dry and moist conditions.
Pacheco M, Bordonhos M, Sardo M, Afonso R, R. B. Gomes J, Mafra L, et al. Moisture effect on the separation of CO2/CH4 mixtures with amine-functionalised porous silicas. Chem Eng J 2022; 443: 136271.
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Sardo M, Afonso R, Juźków J, Pacheco M, Bordonhos M, Pinto ML, et al. Unravelling moisture-induced CO2 chemisorption mechanisms in amine-modified sorbents at the molecular scale. J Mater Chem A 2021; 9: 5542–55.
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