Formation and dehydration enthalpies of gallosilicate materials with different framework topologies and Ga contents

Wei Zhou, Pingping Sun, Alexandra Navrotsky, Seok Han Kim, Suk Bong Hong

Research output: Contribution to journalArticlepeer-review

13 Scopus citations

Abstract

A series of gallosilicate materials with different framework structures (i.e., Ga-MAZ, Ga-OFF, Ga-MOR, TNU-6, and TNU-7) and different Ga contents is investigated by high temperature solution calorimetry in molten lead borate at 700 °C. The dehydration enthalpies for the fully hydrated samples transforming to the partially dehydrated samples, which have 10-20% of the original amount of water remaining, lie in the range 2.0-14.6 kJ per mole of TO2 (T = Si or Ga) and 4.3-24.1 kJ per mole of H2O. The formation enthalpies from oxides of fully hydrated samples range from -87.9 to -4.8 kJ per mole of TO2, while the formation enthalpies of anhydrous samples are estimated to range from -87.9 to +9.8 kJ per mol TO2. The dependence of enthalpies on the framework density and Ga/(Ga + Si) ratio is examined. Similar to trends in aluminosilicate zeolites, high framework density, high T3+ content and large charge balancing cations stabilize gallosilicate materials. Enthalpies of vitrification of gallosilicate crystals are estimated by integrating differential scanning calorimetry (DSC) peaks, and formation enthalpies of gallosilicate glasses are calculated.

Original languageEnglish (US)
Pages (from-to)200-207
Number of pages8
JournalMicroporous and Mesoporous Materials
Volume121
Issue number1-3
DOIs
StatePublished - May 1 2009
Externally publishedYes

Keywords

  • Dehydration enthalpy
  • Formation enthalpy
  • Framework density
  • Gallosilicate materials
  • TG-DSC

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials

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