Two-component model for catalyst deactivation

Texture evolution of alumina hydrotreating catalyst was theoretically modeled using geometrical characteristics calculated via Monte-Carlo methods and methods of the graph theory. In the prescribed model deactivation was specified by monotonic increase of alumina grain radius, which imitated deposition of coke and metal species onto the pore surface. A novel two-component nonhomogeneous model was designed based on the diffusion of asphaltene molecules inside the cylindrical pellet according to Fick's law and deposition of the coke particles from heavy oil on the surface of the catalyst. The model resulted in non-monotonous coke distribution with a distinct maximum in the inner region of the pellet, which, nevertheless, shifts to the center at later deactivation stages due to the higher hydrogenation performance of pellet border region. Model can be applied to describe profiles of coke depositions during deactivation process for a pellet with an arbitrary boundary.