Influence of structural heterogeneity on selectivity in fractal catalyst structures

In the past Monte-Carlo simulations have been used to study the influence o f morphological properties of fractal surfaces on the selectivity between c ompeting three-step catalytic reactions. These simulations were conducted u sing abstract two-dimensional diffusion-limited aggregate models. In an att empt to identify the appropriate properties of a real material that should be represented in a model this previous work has been extended to consider three-dimensional models (cluster-cluster aggregates and the Menger sponge) , in order to correlate selectivity with model characteristics which may be related to input from experimental characterisation data, such as that fro m magnetic resonance imaging. The simulations on three-dimensional models h ave shown that both the porosity and the mass fractal dimension of the mode ls are important to accurately represent a real porous material; a finding not explicit in previous work in two dimensions. (C) 1998 Academic Press.