Nitrogen Adsorption on Silica Surfaces of Nonporous and Mesoporous Materials

We present an accurate comparative analysis of N2 adsorption at 77 K on nonporous silica and the pore wall surface of MCM-41 materials. The analysis shows that in the low-pressure region of N2 adsorption obeys a peculiar mechanism governed by short-ranged forces, which makes the surface curvature ef...

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Bibliographic Details
Published in:Langmuir 2008-07, Vol.24 (13), p.6668-6675
Main Author: Ustinov, Eugene A
Format: Article
Language:English
Subjects:
Interfaces: Adsorption, Reactions, Films, Forces
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Summary:We present an accurate comparative analysis of N2 adsorption at 77 K on nonporous silica and the pore wall surface of MCM-41 materials. The analysis shows that in the low-pressure region of N2 adsorption obeys a peculiar mechanism governed by short-ranged forces, which makes the surface curvature effect on the N2 adsorption in mesopores nearly negligible. We used this observation to define more exactly compared to the BET technique the specific surface area of the reference adsorption isotherm on nonporous silica basing on XRD data and linear sections of t-plots. Calculation of the capillary evaporation and condensation pressures seems to confirm our previous finding that the capillary condensation pressure corresponds to the equilibrium transition rather than spinodal condensation at least for pore sizes less than 7 nm. It allowed us to provide more reliable pore size distribution (PSD) analysis of mesoporous silica materials. For example, the PSDs of MCM-41 samples do not show artificial peaks in the micropore range that we obtained in our earlier publications.
ISSN:0743-7463
1520-5827
DOI:10.1021/la704011z