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Keywords:

  • fractal;
  • alumina;
  • characterisation;
  • and adsorption

Abstract

The classical method for surface characterisation of the porous structure of the catalysts is nitrogen (N2) adsorption at −196°C, which provides a catalyst surface area value valid for molecules similar in size to N2 (0.162 nm2/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