Kinetics of thermal dehydroxylation and carbonation of magnesium hydroxide

Darryl P. Butt, Klaus Lackner, Christopher H. Wendt, Samuel D. Conzone, Harriet Kung, Yung Cheng Lu, Julie K. Bremser

Research output: Contribution to journalArticle

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Abstract

The kinetics of simultaneous dehydroxylation and carbonation of precipitated Mg(OH)2 were studied using isothermal and nonisothermal thermogravimetric analyses. Specimens were analyzed using X-ray diffraction, transmission electron microscopy, and through measurements of the volume of carbon dioxide evolved in a subsequent reaction with hydrochloric acid. From 275° to 475°C, the kinetics of isothermal dehydroxylation in helium were best fit to a contracting-sphere model, yielding an activation energy of 146 kJ/mol, which was greater than values reported in the literature for isothermal dehydroxylation under vacuum (53-126 kJ/mol). The carbonation kinetics were complicated by the fact that dehydroxylation occurred simultaneously. The overall kinetics also could be fit to a contracting-sphere model, yielding a net activation energy of 304 kJ/mol. The most rapid carbonation kinetics occurred near 375°C. At this temperature, Mg(OH)2 underwent rapid dehydroxylation and subsequent phase transformation, whereas thermodynamics favored the formation of carbonate. During carbonation, MgCO3 precipitated on the surface of disrupted Mg(OH)2 crystals acting as a kinetic barrier to both the outward diffusion of H2O and the inward diffusion of CO2.

Original languageEnglish (US)
Pages (from-to)1892-1898
Number of pages7
JournalJournal of the American Ceramic Society
Volume79
Issue number7
StatePublished - Jul 1996
Externally publishedYes

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Magnesium Hydroxide
Carbonation
Magnesium
Kinetics
Activation energy
Helium
Hydrochloric Acid
Carbonates
Hydrochloric acid
Carbon Dioxide
Hot Temperature
Carbon dioxide
Phase transitions
Thermodynamics
Vacuum
Transmission electron microscopy
X ray diffraction
Crystals

ASJC Scopus subject areas

  • Ceramics and Composites

Cite this

Butt, D. P., Lackner, K., Wendt, C. H., Conzone, S. D., Kung, H., Lu, Y. C., & Bremser, J. K. (1996). Kinetics of thermal dehydroxylation and carbonation of magnesium hydroxide. Journal of the American Ceramic Society, 79(7), 1892-1898.

Kinetics of thermal dehydroxylation and carbonation of magnesium hydroxide. / Butt, Darryl P.; Lackner, Klaus; Wendt, Christopher H.; Conzone, Samuel D.; Kung, Harriet; Lu, Yung Cheng; Bremser, Julie K.

In: Journal of the American Ceramic Society, Vol. 79, No. 7, 07.1996, p. 1892-1898.

Research output: Contribution to journalArticle

Butt, DP, Lackner, K, Wendt, CH, Conzone, SD, Kung, H, Lu, YC & Bremser, JK 1996, 'Kinetics of thermal dehydroxylation and carbonation of magnesium hydroxide', Journal of the American Ceramic Society, vol. 79, no. 7, pp. 1892-1898.
Butt, Darryl P. ; Lackner, Klaus ; Wendt, Christopher H. ; Conzone, Samuel D. ; Kung, Harriet ; Lu, Yung Cheng ; Bremser, Julie K. / Kinetics of thermal dehydroxylation and carbonation of magnesium hydroxide. In: Journal of the American Ceramic Society. 1996 ; Vol. 79, No. 7. pp. 1892-1898.
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