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G. Gravogl, Ch. Lengauer, D. Müller, C. Knoll, P. Weinberger, R. Miletich:
"In-situ carbonation of SrO at 298 K and controlled humidity for Thermochemical Energy Storage";
Poster: 32nd European Crystallographic Meeting, Wien; 18.08.2019 - 23.08.2019; in: "Programme Book", Europ. Crystallogr. Assoc. (Hrg.); (2019), S. 66.

In this work the carbonation behavior of SrO under humid conditions was studied through in-situ pXRD measurements at room temperature conditions (298K) with respect to investigate the potential for thermochemical energy storage (TCES). The experiments were performed on a PANalytical X'Pert Pro diffractometer in Bragg-Brentano geometry using CuK_α1,2. An Anton Paar XRK 900 reaction chamber was used monitoring in-situ the reaction. In order to investigate the carbonation in the presence of H₂O saturated conditions the CO₂ was previously passed through an external moisturizer. The study reveals a remarkable carbonation behavior of SrO. As SrO is very hygroscopic it transforms almost immediately to Sr(OH)₂ when getting into contact with the moistened CO₂. It consecutively hydrates yielding Sr(OH)₂·H₂O. Parallel to this hydration a slow continuous carbonation reaction starts which is followed by a significantly accelerated carbonation step after the SrCO₃ phase reached an amount of 10 wt%. This fast carbonation completes the full conversion into SrCO₃ within a short time interval.
We conclude, that the reaction starts at the surface of the particles thus forming a carbonate layer, which retards the CO₂ diffusion into the core of the particles. This is the presumable reason for the slow reaction kinetics at the beginning of the carbonation process. At a certain point the comparatively fast transformation of Sr(OH)₂∙H₂O into SrCO₃ starts, which can be explained by the formation of micro-cracks and microstructural changes including fragmentation of the particles.

thermochemical energy storage, carbonation, strontium oxide