Enthalpies of formation of Ge-zeolites: ITQ-21 and ITQ-22

Qinghua Li, Alexandra Navrotsky, Fernando Rey, Avelino Corma

Research output: Contribution to journalArticlepeer-review

15 Scopus citations

Abstract

A series of Ge-zeolites (ITQ-21 and ITQ-22 with varying Ge content) has been investigated by high-temperature drop solution calorimetry using lead borate solvent at 973 K. The enthalpies of formation relative to a mixture of germania and silica in the quartz forms (ΔHf) at 298 K are in the range 18.9-21.9 kJ/mol. For ITQ-22, the ΔHf values are constant, ∼14.8±0.4 kJ/mol, independent of Ge-content for 0.11 < Ge/(Ge + Si) < 0.24. For ITQ-21, ΔHf becomes progressively more endothermic with increasing Ge content (which corresponds to decreasing framework density or increasing molar volume), similar to the trends seen previously for ITQ-7 and ITQ-17. The relationships between the ΔH f and Ge content for various structures are discussed in terms of concentration of double four membered rings (D4MR) and Ge location in the framework.

Original languageEnglish (US)
Pages (from-to)87-92
Number of pages6
JournalMicroporous and Mesoporous Materials
Volume74
Issue number1-3
DOIs
StatePublished - Sep 20 2004
Externally publishedYes

Keywords

  • Calorimetry
  • Enthalpy of formation
  • Ge-zeolite
  • ITQ-21
  • ITQ-22

ASJC Scopus subject areas

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

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