Kathyola, T.A., Willneff, E.A., Willis, C.J. et al. (2 more authors) (2024) Reactive CaCO3 Formation from CO2 and Methanolic Ca(OH)2 Dispersions: Transient Methoxide Salts, Carbonate Esters and Sol–Gels. ACS Physical Chemistry Au, 4 (5). pp. 555-567. ISSN 2694-2445
Abstract
A combination of ex situ and in situ characterization techniques was used to determine the mechanism of calcium carbonate (CaCO3) formation from calcium hydroxide (Ca(OH)2) dispersions in methanol/water (CH3OH/H2O) systems. Mid-infrared (mid-IR) analysis shows that in the absence of carbon dioxide (CO2) Ca(OH)2 establishes a reaction equilibrium with CH3OH, forming calcium hydroxide methoxide (Ca(OH)(OCH3)) and calcium methoxide (Ca(OCH3)2). Combined ex situ mid-IR, thermogravimetric analysis (TGA), X-ray diffraction (XRD), X-ray absorption spectroscopy and scanning electron microscopy examination of the reaction product formed in the presence of CO2 reveals the formation of calcium dimethylcarbonate (Ca(OCOOCH3)2). This strongly suggests that carbonation takes place by reaction with the Ca(OCH3)2 formed from a Ca(OH)2 and CH3OH reaction. Time-resolved XRD indicates that in the presence of H2O the Ca(OCOOCH3)2 ester releases CH3OH and CO2, forming ACC, which subsequently transforms into vaterite and then calcite. TGA reveals that thermal decomposition of Ca(OCOOCH3)2 in the absence of H2O mainly leads to the reformation of Ca(OCH3)2, but this is accompanied by a significant parallel reaction that releases dimethylether (CH3OCH3) and CO2. CaCO3 is the final product in both decomposition pathways. For CH3OH/H2O mixtures containing more than 50 mol % H2O, direct formation of calcite from Ca(OH)2 becomes the dominant pathway, although the formation of some Ca(OCOOCH3)2 was still evident in the in situ mid-IR spectra of 20 and 40 mol % CH3OH systems. In the presence of ≤20 mol % H2O, hydrolysis of the ester led to the formation of an ACC sol–gel. In both the 90 and 100 mol % CH3OH systems, diffusion-limited ACC → vaterite → calcite transformations were observed. Traces of aragonite were also detected. We believe that this is the first time that these reaction pathways during the carbonation of Ca(OH)2 in a methanolic phase have been systematically and experimentally characterized.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2024 The Authors. This is an open access article under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits unrestricted use, distribution and reproduction in any medium, provided the original work is properly cited. |
Keywords: | calcium carbonate; methanol; reactive crystallization; solvent effects; chemical structure |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Chemical & Process Engineering (Leeds) |
Funding Information: | Funder Grant number EPSRC (Engineering and Physical Sciences Research Council) EP/R511717/1 EPSRC (Engineering and Physical Sciences Research Council) EP/P006965/1 Infineum Ltd PO 4500672762 Diamond Light Source Ltd Diamond House BRAGG Chair Royal Academy of Engineering BRAGG Chair EPSRC (Engineering and Physical Sciences Research Council) EP/P022464/1 |
Depositing User: | Symplectic Publications |
Date Deposited: | 04 Oct 2024 14:59 |
Last Modified: | 04 Oct 2024 14:59 |
Status: | Published |
Publisher: | American Chemical Society |
Identification Number: | 10.1021/acsphyschemau.4c00041 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:217893 |