Pore Size Analysis of MCM-41 Type Adsorbents by Means of Nitrogen and Argon Adsorption

Methods of nonlocal density functional theory (NLDFT), proposed recently for predictions of adsorption equilibrium and calculations of pore size distributions in micro- and mesoporous materials, were tested on reference MCM-41 materials. Five newly synthesized MCM-41 adsorbents with presumably unifo...

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Bibliographic Details
Published in:Journal of colloid and interface science 1998-11, Vol.207 (1), p.159-169
Main Authors: Neimark, Alexander V., Ravikovitch, Peter I., Grün, Michael, Schüth, Ferdi, Unger, Klaus K.
Format: Article
Language:English
Subjects:
Adsorbents
adsorption
capillary condensation
Chemistry
density functional theory
Exact sciences and technology
General and physical chemistry
hysteresis
isosteric heat
MCM-41
pore size distribution
Surface physical chemistry
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Summary:Methods of nonlocal density functional theory (NLDFT), proposed recently for predictions of adsorption equilibrium and calculations of pore size distributions in micro- and mesoporous materials, were tested on reference MCM-41 materials. Five newly synthesized MCM-41 adsorbents with presumably uniform pore channels varying from 32 to 45 Å were characterized by X-ray diffraction (XRD), nitrogen adsorption at 77 K, and argon adsorption at 77 and 87 K. New sets of intermolecular interaction parameters of the NLDFT model for N2and Ar adsorption on MCM-41 were determined. The parameters were specified to reproduce the bulk liquid–gas equilibrium densities and pressures, liquid–gas interfacial tensions, and standard adsorption isotherms on nonporous surfaces in the multilayer adsorption region. The pore size distributions calculated from the desorption branches of the experimental isotherms measured at three different temperatures were consistent with each other. Comparison of the NLDFT-calculated pore sizes with XRD data showed that the thickness of pore walls in the MCM-41 samples under consideration varied from ca. 6 to 12 Å. We found no correlation between the pore size and the pore wall thickness. The results obtained support the NLDFT model as a suitable tool for characterizing nanoporous materials and predicting adsorption equilibrium. The MCM-41 samples studied can be used as references for adsorption measurements.
ISSN:0021-9797
1095-7103
DOI:10.1006/jcis.1998.5748