(502c) Microwave Regeneration of CO2 Solid Sorbent for Energy-Efficient Direct Air Capture

Deployment of energy-efficient regeneration technologies for reagents used in carbon capture is very important in efforts to significantly reduce the high operational cost of direct air capture of CO₂. Guanidine compounds can be used with environmentally friendly aqueous amino acids (e.g., potassium sarcosine) for fast CO₂ capture, and have a strong potential for low-energy CO₂ regeneration. Guanidine compounds [e.g., aqueous 2,6-pyridine-bis(iminoguanidine), PyBIG] react with the CO₂-rich amino acid solution and crystallize as an insoluble carbonate salt [e.g., PyBIGH₂(CO₃)(H₂O)₄]. Separation and thermal regeneration of the precipitated guanidine carbonate salt leads to an overall low-energy direct air capture sorbent. Effective CO₂ release from the solid guanidine compound can be achieved by mild heating at 120°C. In this study, to overcome the relatively inefficient traditional conductive heating of crystallized solids, we evaluated the feasibility of microwave heating of CO₂ loaded guanidine (PyBIGH₂(CO₃)(H₂O)₄) under various operational conditions such as power, radiation time, and solids mass for efficient CO₂ desorption. We found that microwave heating effectively regenerates guanidine carbonate, which may be facilitated by the water molecules that are co-crystallized with guanidine carbonate. These results indicate that microwave regeneration may be an energy-efficient method for the regeneration of solid sorbents used for direct air capture.