Thermochemistry of gallosilicate zeolites with the NAT topology: An energetic view on their in situ disorder-order transformation and thermal stability
SCIE
SCOPUS
- Title
- Thermochemistry of gallosilicate zeolites with the NAT topology: An energetic view on their in situ disorder-order transformation and thermal stability
- Authors
- Zhou, W; Navrotsky, A; Shin, J; Hong, SB
- Date Issued
- 2010-11
- Publisher
- ELSEVIER SCIENCE BV
- Abstract
- The thermochemistry of eight gallosilicate zeolites with the NAT topology, six of which are characterized by similar Ga contents (Si/Ga similar to 1.6) but different T-atom distributions and the other two materials by an unusual higher Ga content (Si/Ga similar to 1.3), is described. The formation enthalpies of the sodium form of gallosilicate natrolites with lower Ga contents (Na-NAT-I, Na-NAT-II and Na-NAT-III) from oxides range from -50.3 to -57.0 kJ mol(-1) of TO2 (T = Si or Ga), while those of the potassium form (K-NAT-I, K-NAT-II and K-NAT-III) lie between -65.5 and -68.4 kJ mol(-1) of TO2. These small energy differences provide a thermodynamic explanation for the in situ transformation between disordered and ordered structures in the crystallization medium. While the formation enthalpy of another potassium natrolite with a high Ga content (K-PST-1) is highly exothermic, consistent with its high thermal stability, its sodium counterpart (Na-PST-1) has a considerable less exothermic formation enthalpy, as well as lower thermal stability. (C) 2010 Elsevier Inc. All rights reserved.
- Keywords
- Gallosilicate zeolites; Natrolite; In situ disorder-order transformation; Formation enthalpy; HYDROTHERMAL SYNTHESIS; DEHYDRATION ENTHALPY; FIBROUS ZEOLITES; NATROLITE; ALUMINUM; GALLIUM; BETA
- URI
- https://oasis.postech.ac.kr/handle/2014.oak/25326
- DOI
- 10.1016/J.MICROMESO.2010.07.004
- ISSN
- 1387-1811
- Article Type
- Article
- Citation
- MICROPOROUS AND MESOPOROUS MATERIALS, vol. 135, no. 1, page. 197 - 200, 2010-11
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