Hydration of MCM-41 Studied by Sorption Calorimetry

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Hydration of MCM-41 Studied by Sorption Calorimetry

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Publication Article, peer reviewed scientific
Title Hydration of MCM-41 Studied by Sorption Calorimetry
Author(s) Kocherbitov, Vitaly ; Alfredsson, Viveka
Date 2007-11-30
English 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 MCM-41 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/cm3. The pore diameter calculated using a combination of X-ray and sorption data is 39 Å. 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.
DOI http://dx.doi.org/10.1021/jp072474r (link to publisher's fulltext)
Host/Issue J. Phys. Chem. C;2007, 111 (35);p. 12906 -12913
Language eng (iso)
Subject(s) MCM-41
Research Subject Categories::NATURAL SCIENCES::Chemistry::Physical chemistry
Research Subject Categories::NATURAL SCIENCES::Chemistry::Physical chemistry::Surface and colloid chemistry
Handle http://pubs.acs.org/cgi-bin/abstract.cgi/jpccck/2007/111/i35/abs/jp072474r.html (link to this page)
http://hdl.handle.net/2043/4590 (link to this page)

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