ARE THE PORE AND SURFACE MORPHOLOGIES OF REAL CATALYSTS FRACTAL

log-log plots of one property vs. another (such as dimension) have bee n employed since the inception of science. Mandelbrot has proposed tha t linear log-log plots with fractional slopes could be characteristic of idealized structures called fractals. Fundamental to these idealize d `fractal' structures is the concept of self-similarity by which spat ial relationships are translated to higher (or lower) dimensions. This paper will assess whether this concept of self-similarity (i.e. fract icality) is applicable to real catalyst pore structures, as has been p roposed and is being exercised extensively in the current theoretical and modelling literature. We analyse the data available for the charac terization of pore structure and compare these data to the properties of idealized fractals. As a specific example, a Menger sponge (an idea lized three-dimensional fractal) is analysed. We find that the void fr actions, adsorption/desorption and Hg porosimetry data for known, prac tical catalysts are inconsistent with a fractal pore network. However, fractal concepts may be useful in our understanding of surface roughn ess. Thus, the bounds on the applications of fractal analyses to real catalysts are placed in perspective. No known industrial catalysts hav e pore structures that can be realistically represented by idealized f ractal structures.