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In situ X-ray diffraction of CaO based CO2 sorbents

DOI: 10.1039/C2EE21779A DOI Help

Authors: R. Molinder (The University of Leeds, U.K.) , T. P. Comyn (The University of Leeds, U.K.) , N. Hondow (The University of Leeds, U.K.) , J. E. Parker (Diamond Light Source) , V. Dupont (The University of Leeds, U.K.)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Energy & Environmental Science , VOL 5 , PAGES 8958-8969

State: Published (Approved)
Published: July 2012
Diamond Proposal Number(s): 2119

Abstract: 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.

Journal Keywords: Carbon Capture

Subject Areas: Energy, Engineering, Materials

Instruments: I11-High Resolution Powder Diffraction