A catalyst deactivation model for residual oil hydrodesulfurization and application to deep hydrodesulfurization of diesel fuel

Hydrodesulfurization processes play a dominant role in the modern refineries to upgrade residual oils either by removing the heterogeneous atoms or by hydrocracking the bottoms to distillate products. A practical model is proposed to predict the catalyst life, which is of great interest to these processes. The catalyst is deactivated in the early stages of the operation by coke deposition on the catalyst's active sites. The ultimate catalyst life is determined by pore mouth plugging depending on its metal capacity. The phenomena are mathematically described by losses of-catalyst surface area and of effective diffusivity of the feedstock molecules in the catalyst pores. The model parameters were collected through pilot plant tests with various types of catalysts and feedstocks. The concept of this model for catalyst deactivation is also applicable to hydrotreating of other petroleum fractions. An example of such applications for the case of deep hydrodesulfurization of diesel fuel is also presented.