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 language | English (US) |
|---|---|
| Pages (from-to) | 1892-1898 |
| Number of pages | 7 |
| Journal | Journal of the American Ceramic Society |
| Volume | 79 |
| Issue number | 7 |
| State | Published - Jul 1996 |
| Externally published | Yes |
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ASJC Scopus subject areas
- Ceramics and Composites
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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 journal › Article
}
TY - JOUR
T1 - Kinetics of thermal dehydroxylation and carbonation of magnesium hydroxide
AU - Butt, Darryl P.
AU - Lackner, Klaus
AU - Wendt, Christopher H.
AU - Conzone, Samuel D.
AU - Kung, Harriet
AU - Lu, Yung Cheng
AU - Bremser, Julie K.
PY - 1996/7
Y1 - 1996/7
N2 - 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.
AB - 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.
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UR - http://www.scopus.com/inward/citedby.url?scp=0030189477&partnerID=8YFLogxK
M3 - Article
AN - SCOPUS:0030189477
VL - 79
SP - 1892
EP - 1898
JO - Journal of the American Ceramic Society
JF - Journal of the American Ceramic Society
SN - 0002-7820
IS - 7
ER -