CO2 capture by functionalized alumina sorbents: DiEthanolAmine on γ-alumina

Alumina-based mesoporous solid sorbents have been successfully prepared in high amount, directly from commercial pellets functionalized with diethanolamine (DEA). The effectiveness of the deposition procedure is confirmed by the detection of diagnostic IR bands characterizing the DEA organic molecule, whose intensity is increasing almost linearly at increasing DEA contents. These materials have shown interesting results in CO2 adsorption both in dry and humid conditions (from12to28mgCO2ads/g), very good resistance to water vapour in the feed and a remarkable regeneration capacity in very mild conditions. Increasing the DEA loading from 15% to 36 wt% resulted in superior capture capacity and useful adsorption time, although the correlation found between DEA content and adsorbed CO2 is less than linear, likely due to a strong interaction between the DEA and the support. Mechanistic spectroscopic IR studies in static conditions point out that CO2 chemisorbs on the amine sites, mainly in form of carbamate species, whose formation should be favoured by the high degree of the surface hydroxylation. On the other side, urea formation is also likely, mainly over samples having the highest DEA content.