In-situ TEM analysis of MgO promoted CaO for CO2 capture

“To capture the structural evolution of the hydrothermally synthesized sorbents during regeneration, in situ TEM was performed on Ca85Mg15 (carbonated state) by heating it up from room temperature to 1100 °C. As shown by the EDX maps of Ca, Mg, and O, provided in Fig. 6a, b, not only the multishelled structure, but also the compositional homogeneity of the sorbent was maintained, even at very high temperatures. It is also noteworthy that although the molar volume of CaCO3 is twice as high as that of CaO, the shrinkage in the diameter of the microsphere after being exposed to 1100 °C was determined to be <15% (Fig. 6c). Considering that the peak associated with carbon disappeared and the oxygen count dropped substantially in the EDX spectra at 1100 °C (Fig. 6d), the limited shrinkage cannot be related to an incomplete conversion of CaCO3 to CaO, but rather to the favorable morphology of the sorbent, which provides sufficient void to accompany substantial volumetric changes during cyclic operations.”


“Thermal stability of the multishelled structure. a STEM/EDX maps of Ca, Mg, and O in Ca85Mg15 acquired in carbonated form at room temperature. b STEM/EDX maps of Ca, Mg, and O in Ca85Mg15 acquired in calcined form at 1100 °C. c Change of the size of a microsphere as a function of temperature. d EDX spectra of Ca85Mg15 before and after calcination. Scale bars: 2 µm”

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