The effects of pore structure on catalyst deactivation by coke formation

Three-dimensional site-bond-site network model was used for simulating the deactivation of catalysts due to poisoning and blockage of pores by coke formation. We have simulated the deactivation of partly amorphous chrome-alumina catalyst during the dehydrogenation of butene to butadiene as well as the deposition of coke in a structured zeolite catalyst ZSM-5 during methanol to gasoline conversion. A simple process rate model is used to describe the deactivation of chrome-alumina catalyst while a detailed Monte-Carlo reaction model is used for methanol conversion giving importance to different aspects like adsorption, desorption, reaction and diffusion. The study shows the importance of morphological and topological characteristics of the pore-structure of the catalyst represented by measurable parameters like: connectivity of network, size distribution of cavities and channels, and correlation of sizes of cavities and channels. The present model correlates more effectively the available experimental deactivation data for the cases studied, both for short and long times and serves as an useful tool for determining the kinetic constants of the deactivation process.