TY - JOUR
T1 - Heat capacity and thermodynamic functions of transition metal ion (Cu2+, Fe2+, Mn2+) exchanged, partially dehydrated zeolite A (LTA)
AU - Dickson, Matthew S.
AU - Rosen, Peter F.
AU - Neilsen, Grace
AU - Navrotsky, Alexandra
AU - Woodfield, Brian F.
N1 - Funding Information:
This work was financially supported by a grant from the U.S. Department of Energy under grant DE-SC0016446. Sample synthesis was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under grant DE-FG02-97ER14749. We thank Xin Guo and Lili Wu for sample synthesis. We would also like to thank Kelsey Heaton and Spencer Shumway for assistance with data analysis and preparation of the manuscript.
Funding Information:
This work was financially supported by a grant from the U.S. Department of Energy under grant DE-SC0016446. Sample synthesis was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under grant DE-FG02-97ER14749. We thank Xin Guo and Lili Wu for sample synthesis. We would also like to thank Kelsey Heaton and Spencer Shumway for assistance with data analysis and preparation of the manuscript.
Publisher Copyright:
© 2021 Elsevier Ltd
PY - 2021/10
Y1 - 2021/10
N2 - We have measured the heat capacity from 1.8 to 300 K of partially dehydrated zeolite A (LTA), fully exchanged with Cu2+, Fe2+, and Mn2+ ions. The samples have a broad excess heat capacity contribution centered around 4 K, which we attribute to local electric fields splitting the magnetic moments of the cations. The excess heat capacity is modelled using a sum of several Schottky anomalies. From these models, we conclude that the cations in the Cu2+ zeolite reside in at least four distinct coordination environments, and that some of the coordination environments in all three zeolites are highly asymmetric. We also report theoretical fits of the heat capacity data, and values of the standard thermodynamic functions CP,m, Δ0KTSm°, Δ0KTHm°, and Φm° at smooth temperatures. The standard molar entropies at 298.15 K are 71.8 J·K−1·mol−1 for Cu-zeolite A (Cu0.22Al0.49Si0.51O2⋅1.04 H2O), 71.1 J·K−1·mol−1 for Fe-zeolite A (Na0.01Fe0.23Al0.50Si0.51O2⋅0.77 H2O), and 66.0 J·K−1·mol−1 for Mn-zeolite A (Mn0.26Al0.49Si0.50O2⋅0.53 H2O).
AB - We have measured the heat capacity from 1.8 to 300 K of partially dehydrated zeolite A (LTA), fully exchanged with Cu2+, Fe2+, and Mn2+ ions. The samples have a broad excess heat capacity contribution centered around 4 K, which we attribute to local electric fields splitting the magnetic moments of the cations. The excess heat capacity is modelled using a sum of several Schottky anomalies. From these models, we conclude that the cations in the Cu2+ zeolite reside in at least four distinct coordination environments, and that some of the coordination environments in all three zeolites are highly asymmetric. We also report theoretical fits of the heat capacity data, and values of the standard thermodynamic functions CP,m, Δ0KTSm°, Δ0KTHm°, and Φm° at smooth temperatures. The standard molar entropies at 298.15 K are 71.8 J·K−1·mol−1 for Cu-zeolite A (Cu0.22Al0.49Si0.51O2⋅1.04 H2O), 71.1 J·K−1·mol−1 for Fe-zeolite A (Na0.01Fe0.23Al0.50Si0.51O2⋅0.77 H2O), and 66.0 J·K−1·mol−1 for Mn-zeolite A (Mn0.26Al0.49Si0.50O2⋅0.53 H2O).
KW - Coordination
KW - LTA
KW - Schottky anomaly
KW - Transition metal
KW - Zeolite A
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U2 - 10.1016/j.jct.2021.106556
DO - 10.1016/j.jct.2021.106556
M3 - Article
AN - SCOPUS:85108406535
SN - 0021-9614
VL - 161
JO - Journal of Chemical Thermodynamics
JF - Journal of Chemical Thermodynamics
M1 - 106556
ER -