Thermochemistry of Microporous and Mesoporous Materials

Navrotsky, Alexandra; Trofymluk, Olga; Levchenko, Andrey A.

doi:10.1021/cr800495t

Cited by 168 publications

(212 citation statements)

References 200 publications

(417 reference statements)

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“…In other words, ACC dehydration is an irreversible process, with the dehydrated form more stable than the hydrated. This behavior is in contrast to the exothermic hydration (with respect to liquid water) of oxides to form oxyhydroxides (43,44), and of dehydrated zeolites to form hydrated ones (45). The DSC measurements indicate that the vaporization of water from synthetic hydrated ACC is endothermic.…”

Section: Discussionmentioning

confidence: 88%

Transformation and crystallization energetics of synthetic and biogenic amorphous calcium carbonate

Radha

Forbes

Killian

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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420

449

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Amorphous calcium carbonate (ACC) is a metastable phase often observed during low temperature inorganic synthesis and biomineralization. ACC transforms with aging or heating into a less hydrated form, and with time crystallizes to calcite or aragonite. The energetics of transformation and crystallization of synthetic and biogenic (extracted from California purple sea urchin larval spicules, Strongylocentrotus purpuratus) ACC were studied using isothermal acid solution calorimetry and differential scanning calorimetry. Transformation and crystallization of ACC can follow an energetically downhill sequence: more metastable hydrated ACC → less metastable hydrated ACC ⇒ anhydrous ACC ∼ biogenic anhydrous ACC ⇒ vaterite → aragonite → calcite. In a given reaction sequence, not all these phases need to occur. The transformations involve a series of ordering, dehydration, and crystallization processes, each lowering the enthalpy (and free energy) of the system, with crystallization of the dehydrated amorphous material lowering the enthalpy the most. ACC is much more metastable with respect to calcite than the crystalline polymorphs vaterite or aragonite. The anhydrous ACC is less metastable than the hydrated, implying that the structural reorganization during dehydration is exothermic and irreversible. Dehydrated synthetic and anhydrous biogenic ACC are similar in enthalpy. The transformation sequence observed in biomineralization could be mainly energetically driven; the first phase deposited is hydrated ACC, which then converts to anhydrous ACC, and finally crystallizes to calcite. The initial formation of ACC may be a first step in the precipitation of calcite under a wide variety of conditions, including geological CO 2 sequestration. amorphous calcium carbonate (ACC) | calorimetry | crystallization enthalpy | sea urchin larval spicules | synthetic and biogenic ACC

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Section: Discussionmentioning

confidence: 88%

Transformation and crystallization energetics of synthetic and biogenic amorphous calcium carbonate

Radha

Forbes

Killian

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

420

449

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“…It may be thought that the latter is a small number, but this depends T angles in the feasibility of zeolites on the efforts dedicated to try to synthesise new zeolites. The narrow differences in their relative free energies [15] is a factor against increasing their number, although some new synthesis methods allow to overcome certain energetic barriers by following a less straight synthesis path [13,14]. Assessing zeolite feasibility is a challenging issue and several attempts have been made [16][17][18].…”

Section: Introductionmentioning

confidence: 99%

The importance of T⋯T⋯T angles in the feasibility of zeolites

Liu

Cubas

Argente

et al. 2015

Zeitschrift Für Kristallographie - Crystalline Materials

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“…Thermochemical data can provide information on stabilities and reactivities of molecules that are used, and also are a key factor in the safe and successful scale-up of chemical processes in the chemical industry. Navrotsky group has done much work on the thermochemistry of microporous compounds such as zeolites, pure silica, gallosilicate, and aluminophosphates by using high-temperature calorimetry [4,5]. Our group has reported the thermodynamic properties of several boron-containing microporous materials [6][7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%