TY - JOUR
T1 - Formation and dehydration enthalpy of ion exchanged zeolite beta
AU - Sun, Pingping
AU - Deore, Suraj
AU - Navrotsky, Alexandra
N1 - Funding Information:
We thank Tricat Zeolites GmbH for sending us well characterized zeolite beta samples, Gregory Baxter and Sarah Roeske for assistance in electron microprobe analysis and Ferenc Forray for computer assistance. This work is supported by National Science Foundation, Grant DMR 0101391.
PY - 2006/4/15
Y1 - 2006/4/15
N2 - Cationic variants of zeolite beta (Li-BEA, Na-BEA, K-BEA, Rb-BEA and Cs-BEA) were prepared via aqueous ion exchange. High-temperature oxide melt solution calorimetry determined the dehydration enthalpy and the formation enthalpy from the constituent oxides. For the alkali cation exchanged zeolites, the total enthalpy of dehydration per mole of zeolite TO2 (T = Si, Al) decreases in magnitude in the order Li-BEA ≈ Na-BEA > K-BEA ≈ Cs-BEA > Rb-BEA. This is in the order of decreasing average ionic potential. The dehydration enthalpy per mole of water decreases in the order Li-BEA > Na-BEA > Cs-BEA > K-BEA > Rb-BEA. The enthalpies of formation become more exothermic with decreasing average ionic potential, as has been observed in several other zeolites. Materials Studio software (Accelrys Inc.) was used to investigate location of the alkali cations and bonding of water molecules in BEA zeolites. The somewhat smaller dehydration enthalpy of K-BEA can be attributed to weaker cation-water interaction, weaker cation-framework interaction, and absence of framework-water interaction.
AB - Cationic variants of zeolite beta (Li-BEA, Na-BEA, K-BEA, Rb-BEA and Cs-BEA) were prepared via aqueous ion exchange. High-temperature oxide melt solution calorimetry determined the dehydration enthalpy and the formation enthalpy from the constituent oxides. For the alkali cation exchanged zeolites, the total enthalpy of dehydration per mole of zeolite TO2 (T = Si, Al) decreases in magnitude in the order Li-BEA ≈ Na-BEA > K-BEA ≈ Cs-BEA > Rb-BEA. This is in the order of decreasing average ionic potential. The dehydration enthalpy per mole of water decreases in the order Li-BEA > Na-BEA > Cs-BEA > K-BEA > Rb-BEA. The enthalpies of formation become more exothermic with decreasing average ionic potential, as has been observed in several other zeolites. Materials Studio software (Accelrys Inc.) was used to investigate location of the alkali cations and bonding of water molecules in BEA zeolites. The somewhat smaller dehydration enthalpy of K-BEA can be attributed to weaker cation-water interaction, weaker cation-framework interaction, and absence of framework-water interaction.
KW - Aqueous ion exchange
KW - Calorimetry
KW - Enthalpy of formation and dehydration
KW - Framework simulation
KW - Zeolite BEA
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U2 - 10.1016/j.micromeso.2005.11.018
DO - 10.1016/j.micromeso.2005.11.018
M3 - Article
AN - SCOPUS:33645059727
SN - 1387-1811
VL - 91
SP - 15
EP - 22
JO - Microporous and Mesoporous Materials
JF - Microporous and Mesoporous Materials
IS - 1-3
ER -