Toward the Development of a Robust Kinetic Model for the Cobalt Fischer-Tropsch Catalyst Lifetime Using a Novel Sigmoidal Pattern

Catalyst deactivation rate greatly depends on many factors including the catalyst structure, reactor feed composition, and operating conditions. Since catalyst deactivation modeling has so far been poorly addressed in the literature, nine experimental sets of cobalt based Fischer-Tropsch catalysts activity-time data were considered to be modeled using an innovative sigmoidal pattern with amazingly meaningful parameters. Such theoretical models for catalyst lifetime significantly facilitate the control of reactors during petrochemical industrial applications, where a constant reactor product flow rate is necessary. Four types of statistics were used to verify the validity of the regression model. The results showed that the proposed model perfectly predicts the activity of the whole catalyst lifetime for a wide range of catalyst types which is capable of being utilized as an important part of a reaction rate. For process conditions within the range of T = 220-230 °C, P = 20 bar, and H2/CO ratio = 2, the average of the two important model constants were: 0.6 ± 0.1 and 0.42 ± 0.06 for steady-state activity and total activity loss, respectively. The proposed model offers a significant advance over the existing macroscopic deactivation models, since different catalyst deactivation trends can be captured.