Phase Evolution and Textural Changes during the Direct Conversion and Storage of CO2 to Produce Calcium Carbonate from Calcium Hydroxide

Abstract

The increasing use of energy resources recovered from subsurface environments and the resulting carbon imbalance in the environment has motivated the need to develop thermodynamically downhill pathways to convert and store CO 2 as water-insoluble calcium or magnesium carbonates. While previous studies extensively explored aqueous routes to produce calcium and magnesium carbonates from CO 2 , there is limited scientific understanding of the phase evolution and textural changes during the direct gas-solid conversion routes to produce calcium carbonate from calcium hydroxide, which is one of the abundant constituents of alkaline industrial residues. With increasing interest in developing integrated pathways for capturing, converting, and storing CO 2 from dilute flue gases, understanding the composition of product phases as they evolve is essential for evaluating the efficacy of a given processing route. Therefore, in this study, we investigate the phase evolution and the corresponding textural changes as calcium hydroxide is converted to calcium carbonate under the continuous flow of CO 2 at an ambient pressure of 1 atm with continuous heating from 30 • C to 500 • C using in-operando wide angle X-ray scattering (WAXS), small angle X-ray scattering (SAXS), and ultrasmall angle X-ray scattering (USAXS) measurements.

Relating Structural and Microstructural Evolution to the Reactivity of Cellulose and Lignin during Alkaline Thermal Treatment with Ca(OH)2 for Sustainable Energy Production Integrated with CO2 Capture

“…In addition to providing insights into the changes in the basal spacing of Ca­(OH) 2 , detailed insights into the changes in the pore–solid interface from the Porod slope were obtained using USAXS/SAXS data. − ,− The Porod slope provides information about the “fractal dimensions” of the scattering objects. In this work, the Porod slope was calculated for the q values in the range 0.02–0.2 Å –1 and the fractality of local structure was investigated.…”

Hybrid Absorption–Crystallization Strategies for the Direct Air Capture of CO2 Using Phase-Changing Guanidium Bases: Insights from in Operando X-ray Scattering and Infrared Spectroscopy Measurements

“…This DAC strategy combines the desirable attributes of aqueous solvents such as fast absorption rates and ease of handling with the minimal sorbent loss characteristic of solid-state sorbents. Furthermore, this coupled CO 2 absorption–crystallization strategy has been successfully applied to accelerate the formation of calcium and magnesium carbonates for the capture and storage of CO 2 . ,,, …”

Increased Sustainability of Carbon Dioxide Mineral Sequestration by a Technology Involving Fly Ash Stabilization

“…This work is mainly based on X-ray diffraction (XRD) analysis, that allows to evaluate the changes of the crystalline phases, due to the carbonation reaction. It was recently shown how in-situ XRD facilities can be very useful to study carbonation [26]. Moreover, in this work, ex-situ XRD was performed, to evaluate amorphous quantification, by the addition of an internal standard.…”