Issue 17, 2015

Energetics of sodium–calcium exchanged zeolite A

Abstract

A series of calcium-exchanged zeolite A samples with different degrees of exchange were prepared. They were characterized by powder X-ray diffraction (XRD) and differential scanning calorimetry (DSC). High temperature oxide melt drop solution calorimetry measured the formation enthalpies of hydrated zeolites CaNa-A from constituent oxides. The water content is a linear function of the degree of exchange, ranging from 20.54% for Na-A to 23.77% for 97.9% CaNa-A. The enthalpies of formation (from oxides) at 25 °C are −74.50 ± 1.21 kJ mol−1 TO2 for hydrated zeolite Na-A and −30.79 ± 1.64 kJ mol−1 TO2 for hydrated zeolite 97.9% CaNa-A. Dehydration enthalpies obtained from differential scanning calorimetry are 32.0 kJ mol−1 H2O for hydrated zeolite Na-A and 20.5 kJ mol−1 H2O for hydrated zeolite 97.9% CaNa-A. Enthalpies of formation of Ca-exchanged zeolites A are less exothermic than for zeolite Na-A. A linear relationship between the formation enthalpy and the extent of calcium substitution was observed. The energetic effect of Ca-exchange on zeolite A is discussed with an emphasis on the complex interactions between the zeolite framework, cations, and water.

Graphical abstract: Energetics of sodium–calcium exchanged zeolite A

Article information

Article type
Paper
Submitted
24 Feb 2015
Accepted
20 Mar 2015
First published
25 Mar 2015

Phys. Chem. Chem. Phys., 2015,17, 11198-11203

Author version available

Energetics of sodium–calcium exchanged zeolite A

H. Sun, D. Wu, X. Guo, B. Shen and A. Navrotsky, Phys. Chem. Chem. Phys., 2015, 17, 11198 DOI: 10.1039/C5CP01133G

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements