Low-Temperature Carbon Capture Using Aqueous Ammonia and Organic Solvents

Current postcombustion CO<sub>2</sub> capture technologies are energy intensive, require high-temperature heat sources, and dramatically increase the cost of power generation. In this work, we introduce a new carbon capture process requiring significantly lower temperatures and less energy, creating further impetus to reduce CO<sub>2</sub> emissions from power generation. In this process, high-purity CO<sub>2</sub> is generated through the addition of an organic solvent (acetone, dimethoxymethane, or acetaldehyde) to a CO<sub>2</sub> rich, aqueous ammonia/carbon dioxide solution under room-temperature and -pressure conditions. The organic solvent and CO<sub>2</sub>-absorbing solution are then regenerated using low-temperature heat. When acetone, dimethoxymethane, or acetaldehyde was added at a concentration of 16.7% (v/v) to 2 M aqueous ammonium bicarbonate, 39.8, 48.6, or 86.5%, respectively, of the aqueous CO<sub>2</sub> species transformed into high-purity CO<sub>2</sub> gas over 3 h. Thermal energy and temperature requirements for recovering acetaldehyde, the best-performing organic solvent investigated, and the CO<sub>2</sub>-absorbing solution were 1.39 MJ/kg of CO<sub>2</sub> generated and 68 °C, respectively, 75% less energy than the amount used in a pilot chilled ammonia process and a temperature 53 °C lower. Our findings exhibit the promise of economically viable carbon capture powered entirely by abundant low-temperature waste heat.