TY - JOUR
T1 - Enthalpies of formation of Ge-zeolites
T2 - ITQ-21 and ITQ-22
AU - Li, Qinghua
AU - Navrotsky, Alexandra
AU - Rey, Fernando
AU - Corma, Avelino
N1 - Funding Information:
This work was supported by the National Science Foundation, (USA) Grant DMR-01-01391 and CICYT, (Spain) project MAT 2000-1392.
PY - 2004/9/20
Y1 - 2004/9/20
N2 - 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.
AB - 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.
KW - Calorimetry
KW - Enthalpy of formation
KW - Ge-zeolite
KW - ITQ-21
KW - ITQ-22
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U2 - 10.1016/j.micromeso.2004.06.010
DO - 10.1016/j.micromeso.2004.06.010
M3 - Article
AN - SCOPUS:4644305034
SN - 1387-1811
VL - 74
SP - 87
EP - 92
JO - Microporous and Mesoporous Materials
JF - Microporous and Mesoporous Materials
IS - 1-3
ER -