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Determination of the fractal dimension of alumina using adsorption: Challenges of choosing appropriate adsorbates and analysis methods
Author(s) -
Capitaine Elsa M. R.,
Hill Josephine M.
Publication year - 2012
Publication title -
the canadian journal of chemical engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.404
H-Index - 67
eISSN - 1939-019X
pISSN - 0008-4034
DOI - 10.1002/cjce.20572
Subject(s) - fractal dimension , adsorption , catalysis , fractal , butane , fractal analysis , molecule , materials science , surface (topology) , thermodynamics , chemical engineering , chemistry , geometry , mathematics , organic chemistry , mathematical analysis , physics , engineering
The classical method for surface characterisation of the porous structure of the catalysts is nitrogen (N 2 ) adsorption at −196°C, which provides a catalyst surface area value valid for molecules similar in size to N 2 (0.162 nm 2 /molecule). To complement and obtain more information about the materials, catalyst surfaces can be characterised using fractal geometry. The fractal dimension of a sample can be determined by the adsorption uptake of molecules of different sizes on the surface of interest in order to obtain a characteristic parameter of the surface geometry known as the fractal dimension, D . In this work, the value of D for a γ‐alumina catalyst support has been determined ( D = 2.71 ± 0.15) using different adsorbates (argon, nitrogen, isopropanol, pyridine, and n ‐butane). The decision process for choosing these adsorbates and the challenges of this type of characterisation method are discussed in this article. © 2011 Canadian Society for Chemical Engineering