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Issue 10, 2012
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In situX-ray diffraction of CaO based CO2 sorbents

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In situ X-ray diffraction coupled with Rietveld refinement has been used to study CO2 capture by CaO, Ca(OH)2 and partially hydrated CaO, as a function of temperature. Phase quantification by Rietveld refinement was performed to monitor the conversion to CaCO3 and the results were compared to those derived using thermogravimetric analysis (TGA). It was found that Ca(OH)2 converted directly to 100% CaCO3 without the formation of a CaO intermediate, at ca. 600 °C. Both pure CaO and partially hydrated CaO (33.6 wt% Ca(OH)2) reached the same capture capacity, containing approximately 65 wt% CaCO3 at 800 °C. It was possible to provide direct evidence of the capture mechanism. The stresses in the Ca(OH)2 phase of the partially hydrated CaO were found to be more than 20 times higher than its strength, leading to disintegration and the generation of nano-sized crystallites. The crystallite size determined using diffraction (75 × 16 nm) was in good agreement with the average crystallite size observed using TEM (of 83 × 16 nm). Electron diffraction patterns confirmed coexistence of CaO and Ca(OH)2. The analysis provides an explanation of the enhanced capture/disintegration observed in CaO in the presence of steam.

Graphical abstract: In situ X-ray diffraction of CaO based CO2 sorbents

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Publication details

The article was received on 28 Mar 2012, accepted on 09 Jul 2012 and first published on 09 Jul 2012

Article type: Paper
DOI: 10.1039/C2EE21779A
Energy Environ. Sci., 2012,5, 8958-8969

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    In situ X-ray diffraction of CaO based CO2 sorbents

    R. Molinder, T. P. Comyn, N. Hondow, J. E. Parker and V. Dupont, Energy Environ. Sci., 2012, 5, 8958
    DOI: 10.1039/C2EE21779A

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