DIFFUSION IN RANDOM PARTICLE MODELS FOR HYDRODEMETALATION CATALYSTS

Recent data showed that it is more realistic to model the structure of hydrotreating catalysts by random spheres instead of cylindrical pores and to model metal depositions by isolated growing crystallites instead of uniform layers. We develop here four progressive models to describe the structure, the average pore radius, the diffusivity, and the relation between percolation threshold and pore plugging. They are (1) the random sphere model, (2) the random needle model, (3) discrete percolation, and (4) continuous random walk.