INTEGRATED REACTIVE CO2 CAPTURE AND CONVERSION TO PRODUCE CALCIUM AND MAGNESIUM CARBONATES

Abstract

More than 82% of our energy needs are being met by fossil-based energy resources, which contribute to about 79% of global CO2 emissions. Designing novel integrated chemical pathways for the capture, conversion, and storage of CO2 is a crucial need for advancing sustainable energy conversion. The accelerated capture, conversion and storage of CO2 as water-insoluble and stable calcium and magnesium carbonates, also known as carbon mineralization, is a promising thermodynamically downhill route. One of the knowledge gaps is a limited understanding of the dynamic chemical and morphological transformation in alkaline calcium and magnesium bearing materials as they are reacted in far-from-equilibrium environments. To address this challenge, synchrotron cross-scale X-ray scattering measurements are harnessed to elucidate simultaneously probe the chemical and morphological evolution of materials in a chemical or thermal reaction environment. Another constraint of carbon mineralization is the slow kinetics at low CO2 concentrations. As a result, there is a significant interest in environmentally benign approaches to capture CO2. One of the less explored but highly transformative approaches to capture CO2 is via coupled absorption-crystallization approaches. This approach addresses the challenge of low solubility of CO2 by using aqueous solvents with high affinity to bind CO2. The resulting carbamate, bicarbonate or carbonate species react with alkaline sources to produce inorganic carbonates while regenerating the solvent. Thermodynamic models are constructed to predict and evaluate the performance of different solvents. Experiments are designed to determine the optimal experimental configurations for integrated reactive CO2 capture and conversion, reaction time, reaction temperature, solvent concentration, and temperature. Our results show that aqueous solvents such as sodium glycinate, MEA, AMP, and DBU are effective in capturing and delivering CO2 to produce calcium or magnesium carbonates at 50-75°C with inherent solvent regeneration. These findings inform the development of intensified approaches to capture and convert CO2 into inorganic carbonates, and represent alternative strategies to regenerate solvents chemically at low temperatures, as an alternative to high temperature thermal regeneration.