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Hydration of MCM-41 studied by sorption calorimetry

Kocherbitov, Vitaly and Alfredsson, Viveka LU (2007) In Journal of Physical Chemistry C 111(35). p.12906-12913
Abstract
Hydration of mesoporous silica MCM-41 was studied using the method of sorption calorimetry. By combining water sorption and nitrogen sorption experiments, we calculated the density of silanol groups on the MCM41 surface as 1.6 nm(-2). Comparison of capillary condensation regimes of water and nitrogen showed that the apparent density of water confined in MCM-41 pores is ca. 0.88 g/cm(3). The pore diameter calculated using a combination of X-ray and sorption data is 39 A. Calculations based on application of the Kelvin-Cohan equation on the water sorption data are in reasonable agreement with this value. The sorption calorimetric results show that the capillary condensation of water in the pores is driven by enthalpy; the entropic effect is... (More)
Hydration of mesoporous silica MCM-41 was studied using the method of sorption calorimetry. By combining water sorption and nitrogen sorption experiments, we calculated the density of silanol groups on the MCM41 surface as 1.6 nm(-2). Comparison of capillary condensation regimes of water and nitrogen showed that the apparent density of water confined in MCM-41 pores is ca. 0.88 g/cm(3). The pore diameter calculated using a combination of X-ray and sorption data is 39 A. Calculations based on application of the Kelvin-Cohan equation on the water sorption data are in reasonable agreement with this value. The sorption calorimetric results show that the capillary condensation of water in the pores is driven by enthalpy; the entropic effect is negative. A mechanism of hydration that involves formation of small unfilled cavities adjacent to pore walls can be used to explain the observed enthalpy end entropy effects. Comparison of sorption and desorption data indicates the presence of air trapped in pores when hydration is performed by mixing MCM-41 with liquid water. The heat effect of pre-capillary condensation adsorption of water on hydroxylated MCM-41 is much more exothermic compared to the original calcined material. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Journal of Physical Chemistry C
volume
111
issue
35
pages
12906 - 12913
publisher
The American Chemical Society
external identifiers
  • wos:000249169900007
  • scopus:34648820025
ISSN
1932-7447
DOI
10.1021/jp072474r
language
English
LU publication?
yes
id
dfc3e2df-f1db-42bb-aa53-a39a0164aec1 (old id 687988)
date added to LUP
2007-12-12 08:38:12
date last changed
2017-09-17 05:35:52
@article{dfc3e2df-f1db-42bb-aa53-a39a0164aec1,
  abstract     = {Hydration of mesoporous silica MCM-41 was studied using the method of sorption calorimetry. By combining water sorption and nitrogen sorption experiments, we calculated the density of silanol groups on the MCM41 surface as 1.6 nm(-2). Comparison of capillary condensation regimes of water and nitrogen showed that the apparent density of water confined in MCM-41 pores is ca. 0.88 g/cm(3). The pore diameter calculated using a combination of X-ray and sorption data is 39 A. Calculations based on application of the Kelvin-Cohan equation on the water sorption data are in reasonable agreement with this value. The sorption calorimetric results show that the capillary condensation of water in the pores is driven by enthalpy; the entropic effect is negative. A mechanism of hydration that involves formation of small unfilled cavities adjacent to pore walls can be used to explain the observed enthalpy end entropy effects. Comparison of sorption and desorption data indicates the presence of air trapped in pores when hydration is performed by mixing MCM-41 with liquid water. The heat effect of pre-capillary condensation adsorption of water on hydroxylated MCM-41 is much more exothermic compared to the original calcined material.},
  author       = {Kocherbitov, Vitaly and Alfredsson, Viveka},
  issn         = {1932-7447},
  language     = {eng},
  number       = {35},
  pages        = {12906--12913},
  publisher    = {The American Chemical Society},
  series       = {Journal of Physical Chemistry C},
  title        = {Hydration of MCM-41 studied by sorption calorimetry},
  url          = {http://dx.doi.org/10.1021/jp072474r},
  volume       = {111},
  year         = {2007},
}