Effect of operating variables on the permanent deactivation of cracking catalyst

Abstract

A mathematical model for the loss of surface area of cracking catalysts in commercial units has been derived from consideration of the rate of coke laydown and the temperature rise due to coke burning. This model is based on and compatible with the extensive laboratory deactivation data. A generalised deactivation rate equation was developed to fit the laboratory data at various temperatures, steam partial pressures, and surface areas. This equation was used in connection with coke-burning calculations to obtain effective deactivation rates and equilibrium surface areas in a commercial unit. In normal operations, the most significant parameters are the difference between coke on spent catalyst and coke on regenerated catalyst and a temperature rise coefficient.