Structure and order in thermal dehydrations of crystalline solids

Galwey, Andrew K.

doi:10.1016/s0040-6031(00)00448-2

Cited by 216 publications

(200 citation statements)

References 160 publications

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“…5 showed that the activation energy values could easily change by 10 kJ/mol and even more, if some experimental points were excluded, most likely due to particle size dispersion in the measured samples [10]. There can be other factors affecting the reaction rate and thus the acti-vation energy values included the self-heating of reaction interface because of exothermic reaction, changes in water vapour concentration in the reaction interface and the diffusion of water to the reaction interface from the surrounding atmosphere [11,12]. These factors are often considered for dehydration reactions because this type of reactions is well characterized, but the same effects may oppositely influence the hydration reactions.…”

Section: Resultsmentioning

confidence: 99%

Hydration of Xylazine Hydrochloride Polymorphic Forms A, Z and M

Krūkle-Bērziņa¹,

Actiņš²,

Be̅rziņš³

2011

Latvian Journal of Chemistry

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Section: Resultsmentioning

confidence: 99%

Hydration of Xylazine Hydrochloride Polymorphic Forms A, Z and M

Krūkle-Bērziņa¹,

Actiņš²,

Be̅rziņš³

2011

Latvian Journal of Chemistry

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“…Several examples of these non-stoichiometric hydrations of APIs are reported. 1,10,11) Some theoretical approaches have also been reported for the dehydration of crystalline solid [12][13][14][15] and thermodynamics of non-stochiometric hydrates. 16) However, investigation of non-stoichiometric hydration is not straightforward because there are various mechanisms that allow APIs to accommodate variable amounts of water.…”

mentioning

confidence: 99%

Characterization of Non-stoichiometric Hydration and the Dehydration Behavior of Sitafloxacin Hydrate

Suzuki

Araki

Kitaoka

et al. 2012

CHEMICAL & PHARMACEUTICAL BULLETIN

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Sitafloxacin (STFX) hydrate is a non-stoichiometric hydrate. The hydration state of STFX hydrate varies non-stoichiometrically depending on the relative humidity and temperature, though X-ray powder diffraction (XRPD) of STFX hydrate was not affected by storing at low and high relative humidities. The detailed properties of crystalline water of STFX hydrate were estimated in terms of hygroscopicity, thermal analysis combined with X-ray powder diffractometry, crystallography and density functional theory (DFT) calculation. STFX hydrate changed the water contents continuously and reversibly from an equivalent amount of dihydrate through that of sesquihydrate depending on the relative humidity at 25°C. Thermal analysis and X-ray powder diffraction (XRPD) simultaneous measurement also revealed that STFX hydrate dehydrated into a hydrated state equivalent to monohydrate by heating up to 100°C, whereas XRPD patterns were slightly affected. This indicated that the crystal structure of STFX hydrate was retained at the dehydration level of monohydrate. Single-crystal X-ray structural analysis showed that two STFX molecules and four water molecule sites were contained in an asymmetric unit. STFX molecules formed a channel structure where water molecules were included. At the partially dehydrated state, at least two of four water molecules were considered to be disordered in occupancy and/or coordinates. Insight into the crystal structure of STFX hydrate stored at low and high relative humidities and geometry of the hydrogen bond were helpful to estimate the origin of non-stoichiometric hydration of STFX hydrate.

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“…Water molecules in ettringite are easily removed because they are simply stabilizing the residual charges of the double hydroxide columns. Therefore, dehydration occurs at temperatures near the boiling point of water [53,54].…”

Section: Resultsmentioning

confidence: 99%

Kinetic and thermal decomposition of ettringite synthesized from aqueous solutions

Guimarães

Oliveira

Leão

2016

J Therm Anal Calorim

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The kinetics of the thermal decomposition of a synthetic ettringite sample was studied between 298 and 820 K in an inert atmosphere for the present work. The ettringite and its thermal decomposition products were characterized using X-ray diffraction, infrared spectroscopy, and scanning electron microscopy. Four endothermic events were observed with thermogravimetry curves, the maxima of which occurred at 366, 397, 537, and 641 K. All events were associated with the loss of water molecules with different degrees of interaction within the ettringite structure. Chemical equations for each decomposition step were proposed based on the percentages of mass loss observed. In addition, for the first time, the activation energies of each ettringite decomposition events were determined by the isoconversional methods of Ozawa-Flynn-Wall, Friedman, and Kissinger-AkahiraSunose. The modeling revealed that the activation energy varied from *50 kJ mol -1 , characteristic of mass transfer control steps, to *150 kJ mol -1 , which is typical of chemical control, as the temperature increased and the ettringite structure lost water. A total of 32 mol of water was released equivalent to 43.1 % of the initial sample mass.

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Structure and order in thermal dehydrations of crystalline solids

Cited by 216 publications

References 160 publications

Hydration of Xylazine Hydrochloride Polymorphic Forms A, Z and M

Hydration of Xylazine Hydrochloride Polymorphic Forms A, Z and M

Characterization of Non-stoichiometric Hydration and the Dehydration Behavior of Sitafloxacin Hydrate

Kinetic and thermal decomposition of ettringite synthesized from aqueous solutions

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