Low-Temperature Regeneration of Amines Integrated with Production of Structure-Controlled Calcium Carbonates for Combined CO2 Capture and Utilization

The CO2 capture process, aimed at mitigation of anthropogenic emission, has conventionally adopted aqueous amine-based absorption. However, amine scrubbing faces some critical barriers such as high energy consumption and chemical degradation due to thermal regeneration. On the other hand, a more promising option for CO2 storage and utilization is mineral carbonation, which not only is the most stable way to store CO2 but also has a variety of applications. To reduce the regeneration of amines and to produce more valuable materials, the question arises whether we can combine the CO2 capture and storage processes in a single unit. This study performed the precipitation-assisted amine regeneration of monoethanolamine (MEA), diethanolamine (DEA), methyl diethanolamine (MDEA), and 2-amino-2-methyl-1-propanol (AMP) solutions and then investigated their CaCO3 polymorphs. The recovery yield of CaCO3 reached about 100% in the MEA solution due to pKa related to CO2 solubility. Using spectroscopic analyses, we revealed the types of amine groups that, when adjacent to the CaCO3 surface, inhibit crystal growth. They can influence crystal growth in ways that lead to the formation of vaterite and/or aragonite, rather than calcite. Moreover, the reaction temperature and supersaturation affected the particle size of CaCO3.