Integration of a diamine solvent based absorption and coal fly ash based mineralisation for CO2 sequestration

Our previous studies have revealed that diamines containing one primary amine group exhibit a superior kinetics while retaining their intrinsic high capacities towards CO2 absorption when compared with monoethanolamine. However, these diamine absorbents typically suffer from high regeneration energy due to the inherent structural stability of the formed carbamate species. In an effort to overcome this challenge, we developed a new CO2 sequestration process that integrates the CO2 absorption by a diamine solvent and the diamine regeneration as well as CO2 mineralization by CaO-rich fly ash. Herein, we found that CO2 rich diamine solutions can be chemically regenerated by fly ash with the stable cyclic performance via the CO2 absorption- mineralization experiments, and the CO2 sequestration capacity of the fly ash used in this process dominated the amine regeneration performance. The FT-IR analysis of species in the solution along with the characterizations of fly ash via SEM, EDX and XRD revealed that fly ash was effective to regenerate a diamine- 1-(2-hydroxyethyl)-4-aminopiperidine (C4) by deprotonation of C4H(+), meanwhile, the CaO component in fly ash can react with CO2 in the C4 solution to produce the calcium carbonate precipitate. This approach presents a significant energy saving alternative to the traditional CO2 desorption process.